Salt and photoresist composition containing the same

ABSTRACT

A salt comprising a group represented by the formula (aa):

This nonprovisional application claims priority under 35 U.S.C. § 119(a)on Patent Application No. 2017-200113 filed in JAPAN on Oct. 16, 2017,the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The invention of the disclosure relates to a salt, and acid generatorcomprising the same, a photoresist composition and a method forproducing a photoresist pattern.

BACKGROUND OF THE INVENTION

US2011/014568A1 mentions the following salt and a photoresistcomposition comprising the same as an acid generator.

JP2013-256496A1 mentions the following salt and a photoresistcomposition comprising the same as an acid generator.

US2017/0247323A1 mentions the following salt and a photoresistcomposition comprising the same as an acid generator.

SUMMARY OF THE INVENTION

The invention of the disclosure relates to the followings:

<1> A salt comprising a group represented by the formula (aa):

wherein X^(a) and X^(b) independently each represent an oxygen atom ora sulfur atom,a ring W represents a C3-C18 heterocycle which has a carbonate esterstructure and which can have a substituent, and* represents a binding position.<2> The salt according to <1>, which comprises a cation and an anionhaving the group represented by formula (aa).<3> The salt according to <2>, wherein the anion having the grouprepresented by formula (aa) further has a sulfonate.<4> The salt according to any one of <1> to <3>, which has a grouprepresented by formula (aa1):

wherein X^(a), X^(b), the ring W and * are as defined above,a ring W1 represents a C3-C18 non-aromatic hydrocarbon ring which canhave a substituent and in which a methylene group can be replaced by—O—, —S—, —CO— or —SO₂—.<5> The salt according to <4>, which has an anion represented by formula(aa2):

wherein X^(a), X^(b), the ring W and the ring W1 are as defined above,L¹ represents a C1-C24 divalent saturated hydrocarbon group in which ahydrogen atom can be replaced by a fluorine atom or a hydroxyl group andin which a methylene group can be replaced by —O— or —CO—, andQ¹ and Q² independently each represent a fluorine atom or a C1-C6perfluoroalkyl group.<6> The salt according to <4> or <5>wherein the ring W1 represents an adamantane ring or a cyclohexane ring.<7> The salt according to <5> or <6>wherein L¹ is represented by formula (b1-1) or (b1-2):

in which L^(b2) represents a single bond or a C1-C22 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom; L^(b3) represents a single bond or a C1-C22 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a hydroxylgroup or a fluorine atom and where a methylene group may be replaced byan oxygen atom or carbonyl group, provided that total number of thecarbon atoms of L^(b2) and L^(b3) is up to 22;L^(b4) represents a C1-C22 divalent saturated hydrocarbon group where ahydrogen atom may be replaced by a fluorine atom; and L^(b5) representsa single bond or a C1-C22 divalent saturated hydrocarbon group where ahydrogen atom may be replaced by a hydroxyl group or a fluorine atom andwhere a methylene group may be replaced by an oxygen atom or carbonylgroup, provided that the total carbon atoms of L^(b4) and L^(b5) is upto 22.<8> The salt according to any one of <1> to <7>wherein the ring W represents 1,3-dioxan-2-one ring.<9> An acid generator comprising the salt according to any one of <1> to<8>.<10> A photoresist composition comprising the acid generator accordingto <9> and a resin which comprises a structural unit having anacid-labile group.<11> The photoresist composition according to <10> which furthercomprises a salt generating an acid weaker in acidity than an acidgenerated from the acid generator.<12> A process for producing a photoresist pattern comprising thefollowing steps (1) to (5):

(1) a step of applying the photoresist composition according to <10> or<11> on a substrate,

(2) a step of forming a composition film by conducting drying,

(3) a step of exposing the composition film to radiation,

(4) a step of baking the exposed composition film, and

(5) a step of developing the baked composition film thereby forming aphotoresist pattern.

DESCRIPTION OF EMBODIMENTS

The salt of the disclosure comprises a group represented by the formula(aa):

wherein X^(a) and X^(b) independently each represent an oxygen atom or asulfur atom,a ring W represents a C3-C18 heterocycle which has a carbonate esterstructure and which can have a substituent, and* represents a binding position.

Herein, the salt of the disclosure is sometimes referred to “Salt (aa)”.

X^(a) and X^(b) are preferably the same one as each other, and morepreferably an oxygen atom.

Preferably, X^(a) and X^(b) are bonded to an identical carbon atom whichthe ring W has.

The ring W represents a C3-C18 heterocycle which has a carbonate esterstructure. For the ring W, the heterocycle may be a monocycle or apolycycle.

Examples of the ring W include 1,3-dioxan-2-one ring, 1,3-dioxolan-2-onering, 1,3-dioxepan-2-one ring, and a fused ring composed of a cycliccarbonate ester and another ring.

The ring W can have a substituent. Examples of a substituent which thering W can have include a hydroxyl group, a cyano group, a carboxylgroup, a C1-C12 alkyl group, a C1-C12 alkoxy group, a C2-C13alkoxycarbonyl group, a C2-C13 acyl group, a C2-C13 acyloxy group, aC3-C12 alicyclic hydrocarbon group, a C6-C12 aromatic hydrocarbon groupand any combination of them.

Examples of the alkyl group include a methyl group, an ethyl group, apropyl group, a butyl group, a pentyl group, a hexyl group, a heptylgroup, an octyl group, a nonyl group, a decyl group, an undecyl groupand a dodecyl group.

Examples of the alkoxy group include a methoxy group, an ethoxy group, apropoxy group, a butoxy group, a pentyloxy group and a hexyloxy group.

Examples of the alicyclic hydrocarbon group include a cyclopentyl group,a cyclohexyl group, an adamantyl group and a norbornyl group.

Examples of the aromatic hydrocarbon group include a phenyl group and anaphthyl group.

Examples of the alkoxycarbonyl group include a methoxycarbonyl group, anethoxycarbonyl group, a propoxycarbonyl group, a butoxycarbonyl group, apentyloxycarbonyl group, a hexyloxycarbonyl group, an octyloxycarbonylgroup, a 2-ethylhexyloxycarbonyl group, a nonyloxycarbonyl group, adecyloxycarbonyl group, an undecyloxycarbonyl group and adodecyloxycarbonyl group.

Examples of the acyl group include an acetyl group, a propionyl groupand butyryl group.

Examples of the acyloxy group include an acetyloxy group, a propionyloxygroup and a butyryloxy group.

Examples of the combinations of these groups include any combinations ofa C1-C12 alkoxy group and a C1-C12 alkyl group, any combinations of ahydroxy group and a C1-C12 alkyl group, any combinations of a C1-C12alkoxy group and a C1-C12 alkoxy group, a combination of a C1-C12 alkoxygroup and a C2-C13 alkylcarbonyl group, and any combinations of a C1-C12alkyl group and a C6-10 aromatic hydrocarbon group.

Examples of the combinations of a C1-C12 alkoxy group and a C1-C12 alkylgroup include a C2-C24 alkoxyalkyl group such as a methoxymethyl group,a methoxyethyl group, an ethoxyethyl group and an ethoxymethyl group.

Examples of the combinations of a C1-C12 alkoxy group and a C1-C12alkoxy group include a C2-C24 alkoxyalkoxy group such as amethoxymethoxy group, a methoxyethoxy group, an ethoxymethoxy group andan ethoxyethoxy group.

Examples of the combinations of a C1-C12 alkoxy group and a C2-C13 acylgroup include a C3-C25 alkoxyalkylcarbonyl group such as a methoxyacetylgroup, a methoxypropionyl group, an ethoxyacetyl group, and anethoxypropionyl group.

Examples of the combinations of a C1-C12 alkoxy group and a C2-C13acyloxy group include a C3-C25 alkoxyacyloxy group such as amethoxyacetyloxy group, a methoxypropionyloxy group, an ethoxyacetyloxygroup, and an ethoxypropionyloxy group.

Examples of the combinations of a C1-C12 alkyl group and a C6-C10aromatic hydrocarbon group include a C7-C22 aralkyl group such as abenzyl group.

The substituent for the ring W is preferably a hydroxyl group, a C1-C12alkoxy group, a C2-C13 acyloxy group, a C2-C24 alkoxyalkyl group, aC2-C24 alkoxyalkoxy group, or a cyano group.

The ring W is preferably a 1,3-dioxan-2-one ring or a 1,3-dioxolan-2-onering, and more preferably a 1,3-dioxan-2-one ring.

The salt preferably has a group represented by formula (aa1):

wherein X^(a), X^(b), the ring W and * are as defined above,a ring W1 represents a C3-C18 non-aromatic hydrocarbon ring which canhave a substituent and in which a methylene group can be replaced by—O—, —S—, —CO— or —SO₂—.

The non-aromatic hydrocarbon ring for the ring W1 may be a monocycle ora polycycle. Specific example of the ring include the groups representedby formulae (W1-1) to (W1-11). The ring is preferably a C3-C12non-aromatic hydrocarbon ring, more preferably a group represented byany one of formulae (W1-1) to (W1-3), and still more preferably a grouprepresented by formulae (W1-1) or (W1-2).

The ring W1 preferably represents an adamantane ring or a cyclohexanering.

The ring W1 can have a substituent. Examples of a substituent which thering W1 can have include a hydroxyl group, a cyano group, a carboxylgroup, a C1-C12 alkyl group, a C1-C12 alkoxy group, a C2-C13alkoxycarbonyl group, a C2-C13 acyl group, a C2-C13 acyloxy group, aC3-C12 alicyclic hydrocarbon group, a C6-C12 aromatic hydrocarbon groupand any combination of them. Specific example of these substituentsinclude the substituents for the ring W as mentioned above.

The substituent for the ring W1 is preferably a hydroxyl group, a cyanogroup, or a C1-C12 alkoxy group, more preferably a hydroxyl group, acyano group, and still more preferably a hydroxyl group. The salt (aa)may have a group represented by formula (aa) either in its anion or inits cation.

The salt (aa) preferably comprises a cation and an anion having thegroup represented by formula (aa), more preferably an organic cation andan anion having the group represented by formula (aa). Preferably, theanion having the group represented by formula (aa) further has asulfonate. More preferably, the anion having the group represented byformula (aa1) further has a sulfonate. The salt (aa) preferablycomprises an anion represented by formula (aa2):

wherein X^(a), X^(b), the ring W and the ring W1 are as defined above,L¹ represents a C1-C24 divalent saturated hydrocarbon group in which ahydrogen atom can be replaced by a fluorine atom or a hydroxyl group andin which a methylene group can be replaced by —O— or —CO—, andQ¹ and Q² independently each represent a fluorine atom or a C1-C6perfluoroalkyl group.

For Q¹ and Q², examples of a perfluoroalkyl group include atrifluoromethyl group, a pentafluoroethyl group, a heptafluoropropylgroup, a nonafluorobutyl group, an undecafluoropentyl group and atridecafluorohexyl group.

Q¹ and Q² each independently preferably represent a fluorine atom or atrifluoromethyl group, and Q¹ and Q² are more preferably fluorine atoms.

For L¹, examples of a C1-C24 divalent saturated hydrocarbon groupinclude a linear or branched chain alkanediyl group, a divalentmonocyclic or polycyclic saturated hydrocarbon group and any combinationof these groups.

Examples of an alkanediyl group include a linear chain alkanediyl groupsuch as a methylene group, an ethylene group, a propane-1,3-diyl group,a butane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diylgroup, a heptane-1,7-diyl group, an octane-1,8-diyl group, anonane-1,9-diyl group, a decane-1,10-diyl group, an undecane-1,11-diylgroup, and dodecane-1,12-diyl group; and a branched chain alkanediylgroup such as ethane-1,1-diyl group, propane-1,1-diyl group,propane-1,2-diyl group, propane-2,2-diyl group, pentane-2,4-diyl group,2-methylpropane-1,3-diyl group, 2-methylpropane-1,2-diyl group,pentane-1,4-diyl group and 2-methylbutane-1,4-diyl group.

Examples of a divalent monocyclic saturatedhydrocarbongroup include acycloalkanediyl group such as a cyclobutane-1,3-diyl group, acyclopentane-1,3-diyl group, a cyclohexane-1,4-diyl group, acyclohexane-3,6-diyl group and a cyclooctane-1,5-diyl group.

Examples of a divalent polycyclic saturated hydrocarbon group include anorbornane-1,4-diyl group, a norbornane-2,5-diyl group, a5-norbornene-2,3-diyl group, an adamantane-1,5-diyl group, andadamantane-2,6-diyl group.

For L¹, examples of the saturated hydrocarbon group in which a methylenegroup has been replaced by an oxygen atom or a carbonyl group includethose represented by formulae (b1-1), (b1-2) and (b1-3).

In formula (b1-1), L^(b2) represents a single bond or a C1-C22 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by afluorine atom, and L^(b3) represents a single bond or a C1-C22 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by ahydroxyl group or a fluorine atom and where a methylene group may bereplaced by an oxygen atom or carbonyl group, provided that total numberof the carbon atoms of L^(b2) and L^(b3) is up to 22.

In formula (b1-2), L^(b4) represents a C1-C22 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom, and L^(b5) represents a single bond or a C1-C22 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a hydroxylgroup or a fluorine atom and where a methylene group may be replaced byan oxygen atom or carbonyl group, provided that the total carbon atomsof L^(b4) and L^(b5) is up to 22.

In formula (b1-3), L^(b6) represents a single bond or a C1-C23 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by afluorine atom, and L^(b7) represents a single bond or a C1-C22 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by ahydroxyl group or a fluorine atom and where a methylene group may bereplaced by an oxygen atom or carbonyl group, with the proviso thattotal carbon number of L^(b6) and L^(b7) is up to 23 and with theproviso that formula (b1-3) excludes a group having a structurerepresented by -L^(b6)-O—CO—.

In these formulae, * represents a binding position to W1.

In formulae (b1-1), (b1-2) and (b1-3), the divalent saturatedhydrocarbon group includes linear chain alkanediyl groups, branchedchain alkanediyl groups, monocyclic or polycyclic divalent saturatedhydrocarbon groups, and a group combining two or more of theabove-mentioned groups.

L^(b2) is preferably a single bond.

L^(b3) is preferably a C1-C4 divalent saturated hydrocarbon group.

L^(b4) is preferably a C1-C8 divalent saturated hydrocarbon group wherea hydrogen atom may be replaced by a fluorine atom.

L^(b5) is preferably a single bond or a C1-C8 divalent saturatedhydrocarbon group.

L^(b6) is preferably a single bond or a C1-C4 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom.

L^(b7) is preferably a single bond or a C1-C7 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a hydroxylgroup or a fluorine atom and where a methylene group may be replaced byan oxygen atom or carbonyl group.

Among them, those of formulae (b1-1) and (b1-2) are preferred.

Examples of the group represented by formula (b1-1) include thoserepresented by formulae (b1-4), (b1-5), (b1-6), (b1-7) and (b1-8).

The group represented by formula (b1-1) is preferably represented byformula (b1-4).

In formula (b1-4), L^(b9) represents a single bond or a C1-C22 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by afluorine atom or a hydroxyl group.

In formula (b1-5), L^(b9) represents a C1-C20 divalent saturatedhydrocarbon group, and L^(b10) represents a single bond or a C1-C19divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a hydroxyl group or a fluorine atom, provided that the totalcarbon atoms of L^(b10) and L^(b9) is up to 20.

In formula (b1-6), L^(b11) represents a C1-C21 divalent saturatedhydrocarbon group, and L^(b12) represents a single bond or a C1-C20divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a hydroxyl group or a fluorine atom, with the proviso thattotal carbon number of L^(b11) and L^(b12) is up to 21.

In formula (b1-7), L^(b13) represents a C1-C19 divalent saturatedhydrocarbon group, L^(b14) represents a single bond or a C1-C18 divalentsaturated hydrocarbon group, and L^(b15) represents a single bond or aC1-C18 divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a hydroxyl group or a fluorine atom, with the proviso thattotal carbon number of L^(b13), L^(b14) and L^(b15) is up to 19.

In formula (b1-8), L^(b16) represents a C1-C18 divalent saturatedhydrocarbon group, L^(b17) represents a C1-C18 divalent saturatedhydrocarbon group, and L^(b18) represents a single bond or a C1-C17divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a hydroxyl group or a fluorine atom, with the proviso thattotal carbon number of L^(b16), L^(b17) and L^(b19) is up to 19.

In these formulae, * represents a binding position to W1.

In these formulae, the divalent saturated hydrocarbon group includeslinear chain alkanediyl groups, branched chain alkanediyl groups,monocyclic or polycyclic divalent saturated hydrocarbon groups, and agroup combining two or more of the above-mentioned groups. Specificexamples of the divalent saturated hydrocarbon group include those asreferred to for L¹.

L^(b8) is preferably a single bond or a C1-C6 divalent saturatedhydrocarbon group such as a C1-C6 alkyl group, more preferably a singlebond or a C1-C4 divalent saturated hydrocarbon group such as a C1-C4alkyl group.

L^(b9) is preferably a C1-C8 divalent saturated hydrocarbon group.

L^(b10) is preferably a single bond or a C1-C19 divalent saturatedhydrocarbon group, and more preferably a single bond or a C1-C8 divalentsaturated hydrocarbon group.

L^(b11) is preferably a C1-C8 divalent saturated hydrocarbon group.

L^(b12) is preferably a single bond or a C1-C8 divalent saturatedhydrocarbon group.

L^(b13) is preferably a C1-C12 divalent saturated hydrocarbon group.

L^(b14) is preferably a single bond or a C1-C6 divalent saturatedhydrocarbon group.

L^(b15) is preferably a single bond or a C1-C18 divalent saturatedhydrocarbon group, and more preferably a single bond or a C1-C8 divalentsaturated hydrocarbon group.

L^(b16) is preferably a C1-C12 divalent saturated hydrocarbon group.

L^(b17) is preferably a C1-C6 divalent saturated hydrocarbon group.

L^(b18) is preferably a single bond or a C1-C17 divalent saturatedhydrocarbon group, and more preferably a single bond or a C1-C4 divalentsaturated hydrocarbon group.

In formula (b1-2), L^(b4) is preferably a C1-C6 divalent saturatedhydrocarbon group such as a C1-C6 alkyl group, more preferably a C1-C4divalent saturated hydrocarbon group such as a C1-C4 alkyl group. L^(b5)is preferably a single bond or a C1-C4 divalent saturated hydrocarbongroup such as a C1-C4 alkyl group, more preferably a single group.

Examples of the group represented by formula (b1-3) include thoserepresented by formulae (b1-9), (b1-10) and (b1-11).

In formula (b1-9), L^(b19) represents a single bond or a C1-C23 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by afluorine atom, and L^(b20) represents a single bond or a C1-C23 divalentsaturated hydrocarbon group where a hydrogen atom may be replaced by ahydroxyl group or a fluorine atom and where a methylene group may bereplaced by an oxygen atom or carbonyl group, provided that the totalcarbon atoms of L^(b19) and L^(b20) is up to 23. In formula (b1-10),L^(b21) represents a single bond or a C1-C21 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom, L^(b22) represents a single bond or a C1-C21 divalent saturatedhydrocarbon group and L^(b23) represents a single bond or a C1-C21divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a hydroxyl group or a fluorine atom and where a methylenegroup may be replaced by an oxygen atom or a carbonyl group, providedthat the total carbon atoms of L^(b21), L^(b22) and L^(b23) is up to 21.

In formula (b1-11), L^(b24) represents a C1-C21 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom, L^(b25) represents a C1-C21 divalent saturated hydrocarbon group,and L^(b26) represents a single bond or a C1-C20 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a hydroxylgroup or a fluorine atom and where a methylene group may be replaced byan oxygen atom or a carbonyl group, provided that the total carbon atomsof L^(b24), L^(b25) and L^(b26) is up to 21.

In these formulae,* represents a binding position to W1.

In these formulae, the divalent saturated hydrocarbon group includeslinear chain alkanediyl groups, branched chain alkanediyl groups,monocyclic or polycyclic divalent saturated hydrocarbon groups, and agroup combining two or more of the above-mentioned groups. Specificexamples of the divalent saturatedhydrocarbongroup include those asreferred to for L¹.

Examples of the divalent saturated hydrocarbon group where a methylenegroup has been replaced by an oxygen atom or a carbonyl group includewhat has an acyloxy group. In what has an acyloxy group, a hydrogen atommay be replaced by a hydroxyl group and a methylene group may bereplaced by an oxygen atom or a carbonyl group.

Examples of what has an acyloxy group include an acetyloxy group, apropionyloxy group, a butyryloxy group, a cyclohexylcarbonyloxy groupand an adamantylcarbonyloxy group.

When a hydrogen atom has been replaced by a hydroxyl group or amethylene group has been replaced by an oxygen atom or a carbonyl groupin what has an acyloxy group, examples of such a group include anoxoadamantylcarbonyloxy group, a hydroxyadamantylcarbonyloxy group, anoxocyclohexylcarbonyloxy group, and a hydroxycyclohexylcarbonyloxygroup.

Examples of the group represented by formula (b1-4) include thefollowing ones.

Examples of the group represented by formula (b1-5) include thefollowing ones.

Examples of the group represented by formula (b1-6) include thefollowing ones.

Examples of the group represented by formula (b1-7) include thefollowing ones.

Examples of the group represented by formula (b1-8) include thefollowing ones.

Examples of the group represented by formula (b1-2) include thefollowing ones.

Examples of the group represented by formula (b1-9) include thefollowing ones.

Examples of the group represented by formula (b1-10) include thefollowing ones.

Examples of the group represented by formula (b1-11) include thefollowing ones.

L¹ represents preferably a group represented by formula (b1-4), morepreferably *1-CO—O—(CH₂)_(t)— where t represents an integer of 0 to 6and *1 is a binding position to *—C(Q¹)(Q²)-. t represents preferably aninteger of 0, 1, or 2, more preferably an integer of 0 or 1.

Specific examples of the anion for Salt (aa) include the following ones.

A cation for Salt (aa) is preferably an organic cation. Examples of theorganic cation include an organic onium cation such as an organicsulfonium cation, an organic iodonium cation, an organic ammoniumcation, a benzothiazolium cation and an organic phosphonium cation.Among them, an organic sulfonium cation and an organic iodonium cationare preferred, and an arylsulfonium cation is more preferred.

Preferred examples of the cation include those represented by theformulae (b2-1), (b2-2), (b2-3) and (b2-4).

In the formulae (b2-1) to (b2-4), R^(b4), R^(b5) and R^(b6)independently represent a C1-C30 aliphatic hydrocarbon group, a C3-C36alicyclic hydrocarbon group and a C6-C36 aromatic hydrocarbon group. Thealiphatic hydrocarbon group can have a substituent selected from thegroup consisting of a hydroxy group, a C1-C12 alkoxy group, a C3-C12alicyclic hydrocarbon group and a C6-C18 aromatic hydrocarbon group. Thealicyclic hydrocarbon group can have a substituent selected from thegroup consisting of a halogen atom, a C1-C18 aliphatic hydrocarbongroup, a C2-C4 acyl group and a glycidyloxy group. The aromatichydrocarbon group can have a substituent selected from the groupconsisting of a halogen atom, a hydroxy group, a C1-C18 aliphatichydrocarbon group and a C1-C12 alkoxy group.

R^(b4) and R^(b5) can be bonded to form a ring together with theadjacent S⁺, and a methylene group in the ring may be replaced by —CO—,—O— or —S—.

R^(b7) and R^(b8) are independently in each occurrence a hydroxy group,a C1-C12 aliphatic hydrocarbon group or a C1-C12 alkoxy group, m2 and n2independently represents an integer of 0 to 5.

R^(b9) and R^(b10) independently represent a C1-C36 aliphatichydrocarbon group or a C3-C36 alicyclic hydrocarbon group.

R^(b9) and R^(b10) can be bonded to form a ring together with theadjacent S⁺, and a methylene group in the divalent alicyclic hydrocarbongroup may be replaced by —CO—, —O— or —S—.

R^(b11) represents a hydrogen atom, a C1-C36 aliphatic hydrocarbongroup, a C3-C36 alicyclic hydrocarbon group or a C6-C18 aromatichydrocarbon group.

R^(b12) represents a C1-C12 aliphatic hydrocarbon group in which ahydrogen atom can be replaced by a C6-C18 aromatic hydrocarbon group, aC3-C18 saturated cyclic hydrocarbon group or a C6-C18 aromatichydrocarbon group in which a hydrogen atom can be replaced by a C1-C12alkoxy group or a (C1-C12 alkyl)carbonyloxy group.

R^(b11) and R^(b12) can be bonded each other to form a C1-C10 divalentalicyclic hydrocarbon group which forms a 2-oxocycloalkyl group togetherwith the adjacent —CHCO—, and a methylene group in the divalentalicyclic hydrocarbon group may be replaced by —CO—, —O— or —S—.

R^(b13), R^(b14), R^(b15), R^(b16), R^(b17) and R^(b18) independentlyrepresent a hydroxy group, a C1-C12 aliphatic hydrocarbon group or aC1-C12 alkoxy group.

L^(b31) represents —S— or —O— and o2, p2, s2 and t2 each independentlyrepresents an integer of 0 to 5, q2 and r2 each independently representsan integer of 0 to 4, and u2 represents 0 or 1.

Preferred examples of the aliphatic hydrocarbon group represented byR^(b4) to R^(b12) include an alkyl group such as a methyl group, anethyl group, a n-propyl group, an isopropyl group, a n-butyl group,sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, anoctyl group and 2-ethylhexyl group. The aliphatic hydrocarbon grouprepresented by R^(b9), R^(b10), R^(b11) and R^(b12) has preferably 1 to12 carbon atoms.

The alicyclic hydrocarbon group may be monocyclic or polycyclic one.Preferred examples of the monocyclic hydrocarbon group include acycloalkyl group such as a cyclopentyl group, a cyclohexyl group, amethylcyclohexyl group, a dimethylcyclohexyl group, a cycloheptyl groupand a cyclooctyl group. Preferred examples of the polycyclic hydrocarbongroup include an adamantyl group, a norbornyl group and adecahydronaphthyl group, and the following groups.

The alicyclic hydrocarbon group represented by R^(b9), R^(b10), R^(b11)and R^(b12) has preferably 3 to 18 carbon atoms, more preferably 4 to 12carbon atoms.

Examples of the alicyclic hydrocarbon group in which a hydrogen atom hasbeen replaced by an aliphatic hydrocarbon group include amethylcyclohexyl group, a dimethylcyclohexyl group, and amethylnorbornyl group.

The alicyclic hydrocarbon group in which a hydrogen atom has beenreplaced by an aliphatic hydrocarbon group has preferably 20 or lesscarbon atoms in total.

Examples of the aromatic hydrocarbon group include an aryl group such asa phenyl group, tolyl group, xylyl group, cumenyl group, mesityl group,p-ethylphenyl group, p-tert-butylphenyl group, p-adamantylphenyl group,a biphenylyl group, a naphthyl group, a phenanthryl group, a2,6-diethylphenyl group, a 2-methyl-6-ethylphenyl group.

When the aromatic hydrocarbon group has an alicyclic hydrocarbon groupor an aliphatic hydrocarbon group, it is preferred that the alicyclichydrocarbon group and the aliphatic hydrocarbon group have respectively1 to 18 carbon atoms and 3 to 18 carbon atoms.

Examples of the aromatic hydrocarbon group in which a hydrogen atom hasbeen replaced by an alkoxy group include p-methoxyphenyl group.

Examples of the aliphatic hydrocarbon group in which a hydrogen atom hasbeen replaced by an aromatic hydrocarbon group include a benzyl group, aphenethyl group, a phenylpropyl group, trityl group, naphthylmethylgroup, and a naphthylethyl group.

Examples of the alkoxy group include a methoxy group, an ethoxy group, apropoxy group, a butoxy group, a pentyloxy group, a hexyloxy group, aheptyloxy group, an octyloxy group, a decyloxy group and a dodecyloxygroup.

Examples of the acyl group include an acetyl group, a propionyl groupand a butyryl group.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

Examples of alkylcarbonyloxy group include a methylcarbonyloxy group, anethylcarbonyloxy group, a n-propylcarbonyloxy group, anisopropylcarbonyloxy group, a n-butylcarbonyloxy group, asec-butylcarbonyloxy group, a tert-butylcarbonyloxy group, apentylcarbonyloxy group, a hexylcarbonyloxy group, an octylcarbonyloxygroup and a 2-ethyl hexylcarbonyloxy group.

The ring group formed by bonding R^(b4) and R^(b5) together with theadjacent S⁺ may be monocyclic or polycyclic, saturated or unsaturated,aromatic or nonaromatic group. The ring is generally 3 to 12-memberedone, preferably 3 to 7-membered one. Examples of the ring include thefollowing ones.

The ring group formed by bonding R^(b9) and R^(b10) together with theadjacent S⁺ may be monocyclic or polycyclic, saturated or unsaturated,aromatic or nonaromatic group. The ring has generally C3-C12, preferablyC3-C7 carbon atoms. Examples of the ring include a thiolan-1-ium ring(tetrahydrothiophenium ring), a thian-1-ium ring and a1,4-oxathian-4-ium ring.

The ring group formed by bonding R^(b11) and R^(b12) together with—CH—CO— may be monocyclic or polycyclic, saturated or unsaturated,aromatic or nonaromatic group. The ring has generally 3 to 12,preferably 3 to 7 carbon atoms. Examples of the ring include anoxocycloheptane ring, an oxocyclohexane ring, an oxonorbornane ring, andan oxoadamantane ring.

Preferred examples of the cation for the acid generator include anarylsulfonium cation, specifically a cation of formula (b2-1). Examplesof the cation represented by the formula (b2-1) include the followings.

Examples of the cation represented by the formula (b2-2) include thefollowings.

Examples of the cation represented by the formula (b2-3) include thefollowings.

Examples of the cation represented by the formula (b2-4) include thefollowings.

Preferably, Salt (aa) is composed of the anion as mentioned above andthe cation as mentioned above. Specific examples of Salt (aa) includethose as listed in following Tables.

In those tables, every character in each column represents a sign whichrepresents one of the chemical formulae specifically illustrated above.For example, the salt (I-1) consists of the anion of formula (I-a-1) andthe cation of formula (b2-c-1) as shown below.

TABLE 1 Salt (aa) anion Cation (I-1) (I-a-1) (b2-c-1) (I-2) (I-a-2)(b2-c-1) (I-3) (I-a-3) (b2-c-1) (I-4) (I-a-4) (b2-c-1) (I-5) (I-a-5)(b2-c-1) (I-6) (I-a-6) (b2-c-1) (I-7) (I-a-7) (b2-c-1) (I-8) (I-a-8)(b2-c-1) (I-9) (I-a-9) (b2-c-1) (I-10) (I-a-10) (b2-c-1) (I-11) (I-a-11)(b2-c-1) (I-12) (I-a-12) (b2-c-1) (I-13) (I-a-1) (b2-c-10) (I-14)(I-a-2) (b2-c-10) (I-15) (I-a-3) (b2-c-10) (I-16) (I-a-4) (b2-c-10)(I-17) (I-a-5) (b2-c-10) (I-18) (I-a-6) (b2-c-10) (I-19) (I-a-7)(b2-c-10) (I-20) (I-a-8) (b2-c-10) (I-21) (I-a-9) (b2-c-10) (I-22)(I-a-10) (b2-c-10) (I-23) (I-a-11) (b2-c-10) (I-24) (I-a-12) (b2-c-10)(I-25) (I-a-1) (b2-c-12) (I-26) (I-a-2) (b2-c-12)

TABLE 2 Salt (aa) anion Cation (I-27) (I-a-3) (b2-c-12) (I-28) (I-a-4)(b2-c-12) (I-29) (I-a-5) (b2-c-12) (I-30) (I-a-6) (b2-c-12) (I-31)(I-a-7) (b2-c-12) (I-32) (I-a-8) (b2-c-12) (I-33) (I-a-9) (b2-c-12)(I-34) (I-a-10) (b2-c-12) (I-35) (I-a-11) (b2-c-12) (I-36) (I-a-12)(b2-c-12) (I-37) (I-a-1) (b2-c-14) (I-38) (I-a-2) (b2-c-14) (I-39)(I-a-3) (b2-c-14) (I-40) (I-a-4) (b2-c-14) (I-41) (I-a-5) (b2-c-14)(I-42) (I-a-6) (b2-c-14) (I-43) (I-a-7) (b2-c-14) (I-44) (I-a-8)(b2-c-14) (I-45) (I-a-9) (b2-c-14) (I-46) (I-a-10) (b2-c-14) (I-47)(I-a-11) (b2-c-14) (I-48) (I-a-12) (b2-c-14) (I-49) (I-a-1) (b2-c-27)(I-50) (I-a-2) (b2-c-27) (I-51) (I-a-3) (b2-c-27) (I-52) (I-a-4)(b2-c-27) (I-53) (I-a-5) (b2-c-27) (I-54) (I-a-6) (b2-c-27) (I-55)(I-a-7) (b2-c-27) (I-56) (I-a-8) (b2-c-27) (I-57) (I-a-9) (b2-c-27)(I-58) (I-a-10) (b2-c-27) (I-59) (I-a-11) (b2-c-27) (I-60) (I-a-12)(b2-c-27) (I-61) (I-a-1) (b2-c-30) (I-62) (I-a-2) (b2-c-30) (I-63)(I-a-3) (b2-c-30) (I-64) (I-a-4) (b2-c-30) (I-65) (I-a-5) (b2-c-30)(I-66) (I-a-6) (b2-c-30) (I-67) (I-a-7) (b2-c-30) (I-68) (I-a-8)(b2-c-30) (I-69) (I-a-9) (b2-c-30) (I-70) (I-a-10) (b2-c-30) (I-71)(I-a-11) (b2-c-30) (I-72) (I-a-12) (b2-c-30) (I-73) (I-a-1) (b2-c-31)(I-74) (I-a-1) (b2-c-31) (I-75) (I-a-2) (b2-c-31) (I-76) (I-a-3)(b2-c-31) (I-77) (I-a-4) (b2-c-31) (I-78) (I-a-5) (b2-c-31) (I-78)(I-a-6) (b2-c-31)

TABLE 3 Salt (aa) anion Cation (I-79) (I-a-7) (b2-c-31) (I-80) (I-a-8)(b2-c-31) (I-81) (I-a-9) (b2-c-31) (I-82) (I-a-10) (b2-c-31) (I-83)(I-a-11) (b2-c-31) (I-84) (I-a-12) (b2-c-31)

Among these specific examples, preferred as Salt (aa) are salt(I-1),salt(I-5), salt(I-10), salt(I-11), salt(I-12), salt(I-13), salt(I-17),salt(I-22), salt(I-23), salt(I-24), salt(I-25), salt(I-29), salt(I-34),salt(I-35), salt(I-36), salt(I-37), salt(I-41), salt(I-46), salt(I-47),salt(I-48), salt(I-49), salt(I-53), salt(I-58), salt(I-59), salt(I-60),salt(I-61), salt(I-65), salt(I-70), salt(I-71), salt(I-72), salt(I-73),salt(I-77), salt(I-82), salt(I-83) and salt(I-84).

When Salt (aa) is composed of an anion represented by formula (aa2) andan organic cation, the salt can be produced by reacting a saltrepresented by the formula (aa-a) with the compound represented byformula (aa-b), in the presence of a base such as pyridine in a solventsuch as chloroform or acetonitrile:

wherein Q¹, Q², L¹, W1, X^(a) and X^(b) are the same as defined above,Z⁺ represents an organic cation, and L¹¹ and L¹² each independentlyrepresent a C1-C6 alkanediyl group or a single bond.

The above-mentioned reaction is usually conducted at about 5 to 200° C.,preferably at about 50 to 150° C.

The salt represented by the formula (aa-a) can be produced by reacting asalt represented by the formula (aa-c) with the compound represented byformula (aa-d), in the presence of an acid catalyst such asp-toluenesulfonic acid in a solvent such as dimethylformamide,chloroform or acetonitrile:

wherein Q¹, Q², L¹, W1, X^(a), X^(b), L¹¹ and L¹² are the same asdefined above.

Specific examples of the salt represented by the formula (aa-c) includethe following ones. These salts can be prepared according to a method asrecited in JP2007-224008A1, JP2011-116747A1 or JP2012-224611A1.

Specific examples of the compound represented by the formula (aa-d)include the following ones. The compound represented by the formula(aa-d) is available on the market.

<Acid Generator>

The acid generator of the disclosure comprises Salt (aa). The acidgenerator may contain two or more kinds of Salt (aa). The acid generatormay further contain one or more known acid generator in addition to Salt(aa).

In the photoresist composition, an acid generates from the acidgenerator by light for lithography. The acid catalytically acts againstan acid-labile group in the resin to cleave the acid-labile group.

The acid generator known in the art may be a nonionic acid generator oran ionic acid generator. Examples of the nonionic acid generator includean organo-halogen compound, a sulfonate compound such as a2-nitrobenzylsulfonate, an aromatic sulfonate, an oxime sulfonate, anN-sulfonyloxyimide, a sulfonyloxyketone and diazonaphthoquinone4-sulfonate, and a sulfone compound such as a disulfone, a ketosulfoneand a sulfonyldiazomethane. Examples of the ionic acid generator includean onium salt compound such as a diazonium salt, a phosphonium salt, asulfonium salt and an iodonium salt. Examples of the anion of the oniumsalt include a sulfonic acid anion, a sulfonylimide anion and asulfonylmethide anion.

Specific examples of the acid generator known in the art include acidgenerators described in JP 63-26653 A, JP 55-164824 A, JP62-69263 A,JP63-146038A, JP63-163452A, JP62-153853A, JP63-146029A, U.S. Pat. Nos.3,779,778, 3,849,137, DE Patent No. 3914407 and EP Patent No. 126,712.Other examples of that include acid generators described inJP2013-68914A, JP2013-3155A and JP2013-11905A.

The acid generator known in the art is preferably a fluorine-containingacid generator, and more preferably a fluorine-containing organicsulfonate acid generator.

Preferable examples of the acid generator known in the art include asalt represented by the formula (B1):

wherein Q^(b1) and Q^(b2) each independently represent a fluorine atomor a C1-C6 perfluoroalkyl group,

L^(b1) represents a C1-C24 divalent saturated hydrocarbon group in whicha methylene group can be replaced by —O— or —CO— and in which a hydrogenatom can be replaced by a fluorine atom or a hydroxy group, and

Y represents a methyl group which can have a substituent or a C3-C18monovalent alicyclic hydrocarbon group which can have a substituent andin which a methylene group can be replaced by —O—, —CO— or —SO₂—, and

Z1⁺ represents an organic cation.

Hereinafter, the salt represented by the formula (B1) is sometimesreferred to as “Salt (B1)”.

For Q^(b1) and Q^(b2), examples of the perfluoroalkyl group includeexamples of those for Q¹ and Q², and a trifluoromethyl group ispreferred.

Q^(b1) and Q^(b2) each independently preferably represent a fluorineatom or a trifluoromethyl group, and Q^(b1) and Q^(b2) are morepreferably fluorine atoms.

For L^(b1), examples of a C1-C24 divalent saturated hydrocarbon groupinclude an alkanediyl group, a divalent monocyclic or polycyclicsaturated hydrocarbon group and any combination of these groups.Specific examples of the divalent saturatedhydrocarbongroup includethose as the saturated hydrocarbon group represented by L¹.

For L^(b1), examples of the saturated hydrocarbon group in which amethylene group has been replaced by an oxygen atom or a carbonyl groupinclude those represented by formulae (b1-1), (b1-2) and (b1-3), asmentioned above.

In these formulae for L^(b1), * represents a binding position to Y.Among them, those of formulae (b1-1) and (b1-3) are preferred.

Examples of the group represented by formula (b1-1) include thoserepresented by formulae (b1-4), (b1-5), (b1-6), (b1-7) and (b1-8), asmentioned above.

In these formulae for L^(b1), * represents a binding position to Y.

Examples of the group represented by formula (b1-3) include thoserepresented by formulae (b1-9), (b1-10) and (b1-11).

In these formulae for L^(b1), * represents a binding position to Y. ForL^(b1), specific examples of the group represented by formulae (b1-4) to(b1-11) include those as mentioned above, except that * represents abinding position to Y.

The monovalent alicyclic hydrocarbon group for Y may be a monocyclic oneor polycyclic one such as a spiro ring.

Preferred examples of the alicyclic hydrocarbon group represented by Yinclude those represented by the formulae (Y1) to (Y11) and (Y36) to(Y38). Preferred examples of the alicyclic hydrocarbon group which isrepresented by Y and in which a methylene group has been replaced by—O—, —SO₂— or —CO— include those represented by the formulae (Y12) to(Y35) and (Y39) to (Y41).

Among the groups represented by the formulae, preferred are thoserepresented by formulae (Y1) to (Y20), (Y30), (Y31), (Y39) and (Y41);more preferred are those represented by the formulae (Y11), (Y15),(Y16), (Y20), (Y30), (Y31), (Y39) and (Y40); and still more preferredare those represented by the formulae (Y11), (Y15), (Y30), (Y39) and(Y40).

When Y has a spiro ring such as the groups represented by formulae (Y28)to (Y35), (Y39) and (Y40), the spiro ring preferably has a fluorine atomon an alkanediyl between two oxygen atoms. Furthermore, a methylenegroup attached to an oxygen atom in an alkanediyl group forming a ketalstructure has not been replaced by a fluorine atom.

Substituents on the methyl group for Y include a halogen atom, ahydroxyl group, a C3-C16 alicyclic hydrocarbon group, a C6-C18 aromatichydrocarbon group, a glycidyloxy group, and —(CH₂)_(j2)—O—CO—R^(b1′)— inwhich R^(b1′) is a C1-C16 alkyl group and j2 is an integer of 0 to 4.

Substituents on the alicyclic hydrocarbon groups for Y include a halogenatom, a hydroxyl group, a C1-C12 alkyl group, a C1-C12hydroxy-containing alkyl group, a C1-C12 alkoxy group, a C3-C16alicyclic hydrocarbon group, a C6-C18 aromatic hydrocarbon group, aC7-C21 aralkyl group, a C2-C4 acyl group, a glycidyloxy group, and—(CH₂)_(j2)—O—CO—R^(b1′)— in which R^(b1′) is a C1-C16 alkyl group andj2 is an integer of 0 to 4.

Substituents on the alicyclic hydrocarbon group for Y does not have acarbonate ester structure.

Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

Examples of the alicyclic hydrocarbon group include a cyclopentyl group,a cyclohexyl group, a cycloheptyl group and a cyclooctyl group, anorbornyl group and an adamantyl group.

Examples of the aromatic hydrocarbon group include an aryl group such asa phenyl group, a naphthyl group, an anthryl group, a p-methylphenylgroup, a p-tert-butylphenyl group, a p-adamantylphenyl group, a tolylgroup, a xylyl group, a cumyl group, a mesityl group, a biphenyl group,a phenanthryl group, a 2,6-diethylphenyl group and a2-methyl-6-ethylphenyl group.

Examples of the alkyl group include a methyl group, an ethyl group, apropyl group, an isopropyl group, a butyl group, a sec-butyl group, atert-butyl group, a pentyl group, a hexyl group, a heptyl group, a2-ethylhexyl group and a dodecyl group.

Examples of hydroxyl-containing alkyl group include a hydroxymethylgroup and a hydroxyethyl group.

Examples of the C1-C12 alkoxy group include a methoxy group, an ethoxygroup, a propoxy group, a butoxy group, a pentyloxy group, a hexyloxygroup, a heptyloxy group, an octyloxy group, a decyloxy group and adodecyloxy group.

Examples of the aralkyl group include a benzyl group, phenylpropylgroup, a phenethyl group, a naphthylmethyl group, or a naphthylethylgroup.

Examples of the acyl group include an acetyl group, a propionyl groupand a butyryl group.

Examples of Y include the groups as follow.

Y represents preferably a C3-C18 alicyclic hydrocarbon group which mayhave a substituent and in which a methylene group has been replaced by—O—, —SO₂— or —CO—, more preferably an adamantyl group which may have asubstituent and in which a methylene group has been replaced by —O—,—SO₂— or —CO—, and still more preferably an adamantyl group, ahydroxyadamantyl group, an oxoadamantyl group, or the following group.

where * represents a binding position.

Preferred examples of the sulfonic acid anion of the salt represented byformula (B1) include salts represented by the formulae (B1-A-1) to(B1-A-55), preferably the formulae (B1-A-1) to (B1-A-4), (B1-A-9),(B1-A-10), (B1-A-24) to (B1-A-33), (B1-A-36) to (B1-A-40) and (B1-A-47)to (B1-A-55).

In these formulae, the symbols Q^(b1) and Q^(b2) are defined as above,R^(i2), R^(i3), R^(i4), R^(i5), R^(i6) and R^(i7) each independentlyrepresent a C1-C4 alkyl group, preferably a methyl group or an ethylgroup, R^(i8) represents a C1-C12 aliphatic hydrocarbon group[preferably a C1-C4 alkyl group], a C5-C12 monovalent alicyclichydrocarbon group, or a combined group of them, preferably a methylgroup, an ethyl group, a cyclohexyl group or an adamantyl group, andL^(A4) represents a single bond or a C1-C4 alkanediyl group.

Examples of the sulfonic acid anion of the salt represented by formula(B1) include those described in JP2010-204646A1.

Specific examples of the anion for the salt represented by formula (B1)include the following anions.

Among them, preferred are those represented by formulae (B1a-1) to(B1a-3), (B1a-7) to (B1a-16), (B1a-18), (B1a-19) and (B1a-22) to(B1a-34).

Examples of the organic ion represented by Z1⁺ include an onium cationsuch as a sulfonium cation, an iodonium cation, an ammonium cation, abenzothiazolium cation and a phosphonium cation, specifically thecations represented by formulae (b2-1) to (b2-4). The salt representedby formula (B1) is preferably a salt which consists of an anionrepresented by any one of formulae (B1a-1) to (B1a-3), (B1a-7) to(B1a-16), (B1a-18), (B1a-19) and (B1a-22) to (B1a-34) with a cationrepresented by formula (b2-1) or (b2-3). Specific examples of the saltrepresented by formula (B1) include the following salts represented byformulae (B1-1) to (B1-48). Among them, those which comprise anarylsulfonium cation are preferred, the salts represented by formulae(B1-1) to (B1-3), (B1-5) to (B1-7), (B1-11) to (B1-14), (B1-20) to(B1-26), (B1-29), (B1-31) to (B1-48) are more preferred.

When the acid generator contains another salt than the salt (aa), theweight ratio of salt (aa) and the other salts is usually 1:99 to 99:1,preferably 2:98 to 98:2, more preferably 5:95 to 95:5, still morepreferably 10:90 to 90:10, and further more preferably 15:85 to 85:15.

The photoresist composition of the disclosure comprises the acidgenerator containing Salt (aa) and a resin having an acid-labile groupwhich resin is referred to as “Resin (A)”.

The photoresist composition may further contain another salt than Salt(aa) as an acid generator, a quencher, or solvent.

The content of the acid generator is preferably 1 to 40 parts by mass,more preferably 3 to 35 parts by mass, per 100 parts of Resin (A).

Resin (A) usually has a structural unit having an acid-labile group.Hereinafter, the structural unit is sometimes referred to as “structuralunit (a1)”.

Preferably Resin (A) further has another structural unit than thestructural unit (a1), i.e. a structural unit having no acid-labilegroup, which is sometimes referred to as “structural unit (s)”. Herein,“an acid-labile group” means a group which has a hydrophilic group, suchas a hydroxy group or a carboxy group, resulting from removing a leavinggroup therefrom by the action of an acid.

<Structural Unit (a1)>

The structural unit (a1) is derived from a compound having anacid-labile group which compound is sometimes referred to as “Monomer(a1)”.

For Resin (A), the acid-labile groups represented by formulae (1) and(2) are preferred.

In formula (1), R^(a1), R^(a2) and R^(a3) independently each represent aC1-C8 alkyl group, a C3-C20 alicyclic hydrocarbon group or a groupconsisting of them, and R^(a1) and R^(a2) can be bonded each other toform a C3-C20 alicyclic hydrocarbon group together with the carbon atomto which R^(a1) and R^(a2) are bonded, “na” and “ma” each represent aninteger of 0 or 1 provided that at least one of them represents 1, and *represents a binding position.

In formula (2), R^(a1′) and R^(a2′) independently each represent ahydrogen atom or a C1-C12 hydrocarbon group, and R^(a3′) represents aC1-C20 hydrocarbon group, and R^(a2′) and R^(a3′) can be bonded eachother to form a C3-C20 heterocyclic group together with X and the carbonatom to which R^(a2′) and R^(a3′) are bonded, and one or more —CH₂— inthe hydrocarbon group and the heterocyclic group can be replaced by —O—or —S—, X represents an oxygen atom or a sulfur atom, “na′” representsan integer of 0 or 1, and * represents a binding position. For R^(a1),R^(a2) and R^(a3), specific examples of the alkyl group include a methylgroup, an ethyl group, a propyl group, an isopropyl group, a butylgroup, a pentyl group, a hexyl group, a heptyl group and an octyl group.

The alicyclic hydrocarbon group may be monocyclic or polycyclic.Examples of the alicyclic hydrocarbon group include a monocyclicalicyclic hydrocarbon group such as a C3-C20 cycloalkyl group (e.g. acyclopentyl group, a cyclohexyl group, a cycloheptyl group and acyclooctyl group) and a polycyclic alicyclic hydrocarbon group such as adecahydronaphthyl group, an adamantyl group, a norbornyl group, and thefollowings:

in which * represents a binding position.

The alicyclic hydrocarbon group preferably has 3 to 16 carbon atoms.

Examples of the group consisting of alkyl and alicyclic hydrocarbongroup include a methylcyclohexyl group, a dimethylcyclohexyl group, amethylnorbornyl group, an adamantylmethyl group, and a norbornylethylgroup.

The “ma” is preferably 0. The “na” is preferably 1.

When the divalent hydrocarbon group is formed by bonding R^(a1) andR^(a2) each other, examples of the moiety —C(R^(a1))(R^(a2))(R^(a3))include the following groups and the divalent hydrocarbon grouppreferably has 3 to 12 carbon atoms.

wherein R^(a3) is the same as defined above and * represents a bindingposition.

For formula (2), examples of the hydrocarbon group include an alkylgroup, an alicyclic hydrocarbon group, an aromatic hydrocarbon group anda group consisting of two or more of them.

Examples of the aliphatic hydrocarbon group and the alicyclichydrocarbon group include the same as described above. Examples of thearomatic hydrocarbon group include an aryl group such as a phenyl group,a naphthyl group, a p-methylphenyl group, a p-tert-butylphenyl group, ap-adamantylphenyl group, a tolyl group, a xylyl group, a cumyl group, amesityl group, a biphenyl group, an anthryl group, a phenanthryl group,a 2,6-diethylphenyl group and a 2-methyl-6-ethylphenyl group.

Examples of the heterocyclic group formed by bonding R^(a2′) and R^(a3′)together with X and the carbon atom to which R^(a2′) and R^(a3′) arebonded include the following ones.

wherein * represents a binding position.

In formula (2), at least one of R^(a1′) and R^(a2′) is preferably ahydrogen atom. The “na” is preferably 0.

Examples of the group represented by formula (1) include the followingones:

The group represented by formula (1) wherein R^(a1), R^(a2) and R^(a3)independently each represent a C1-C8 alkyl group, ma is 0, and na is 1,such as a tert-butyl group;

The group represented by formula (1) wherein R^(a1) and R^(a2) arebonded each other to form an adamantyl ring, R^(a3) is a C1-C8 alkylgroup, ma is 0, and na is 1, such as a 2-alkyl-2-adamantyl group;

The group represented by formula (1) wherein R^(a1) and R^(a2) are C1-C8alkyl groups, R^(a3) is an adamantyl group, ma is 0, and na is 1, suchas a 1-(1-adamantyl)-1-alkylalkoxycarbonyl group.

Specific examples of the group represented by formula (1) include thefollowings.

Specific examples of the group represented by formula (2) include thefollowings.

Monomer (a1) is preferably a monomer having an acid-labile group in itsside chain and an ethylenic unsaturated group, more preferably a(meth)acrylate monomer having an acid-labile group in its side chain,and still more preferably a (meth)acrylate monomer having the grouprepresented by formula (1) or (2).

The (meth)acrylate monomer having an acid-labile group in its side chainis preferably those which comprise a C5-C20 alicyclic hydrocarbon group.The resin which comprises a structural unit derived from such monomerscan provide improved resolution for a photoresist pattern to be preparedtherefrom.

The structural unit derived from a (meth)acrylate monomer having thegroup represented by formula (1) is preferably one of structural unitsrepresented by formulae (a1-0), (a1-1) and (a1-2).

In each formula, L^(a01), L^(a1) and L^(a2) each independently represent—O— or *—O—(CH₂)_(k1)—CO—O— in which k1 represents an integer of 1 to 7and * represents a binding position to —CO—,

R^(a01), R^(a4) and R^(a5) each independently represent a hydrogen atomor a methyl group,

R^(a02), R^(a03), R^(a04), R^(a6) and R^(a7) each independentlyrepresent a C1-C8 alkyl group, a C3-C18 alicyclic hydrocarbon group, ora group formed by combining them,

m1 represents an integer of 0 to 14,

n1 represents an integer of 0 to 10, and

n1′ represents an integer of 0 to 3.

Hereinafter, the structural units represented by formulae (a1-0), (a1-1)and (a1-2) are referred to as “structural unit (a1-0)”, “structural unit(a1-1)” and “structural unit (a1-2)”, respectively. Resin (A) maycomprise two or more of such structural units.

L^(a01) is preferably *—O— or *—O—(CH₂)_(f1)—CO—O— in which * representsa binding position to —CO—, and f1 represents an integer of 1 to 4, andis more preferably *—O— or *—O—CH₂—CO—O—, and is especially preferably*—O—.

R^(a01) is preferably a methyl group.

For R^(a02), R^(a03) and R^(a04), examples of the alkyl group, thealicyclic hydrocarbon group and the group formed by combining theminclude the same as referred for R^(a1), R^(a2) and R^(a3).

The alkyl group preferably has 1 to 6 carbon atoms.

The alicyclic hydrocarbon group preferably has 3 to 8 carbon atoms andmore preferably 3 to 6 carbon atoms. The alicyclic hydrocarbon group ispreferably a saturated aliphatic cyclic hydrocarbon group.

The group formed by combining them preferably has 18 carbon atoms orless in total, examples of which include a methylcyclohexyl group, adimethylcyclohexyl group, and a methylnorbornyl group.

Each of R^(a02) and R^(a03) is preferably a C1-C6 alkyl group, morepreferably a methyl group and an ethyl group.

R^(a04) is preferably a C1-C6 alkyl group and a C5-C12 alicyclichydrocarbon group, more preferably a methyl group, an ethyl group, acyclohexyl group, and an adamantyl group.

Each of L^(a1) and L^(a2) is preferably *—O— or *—O—(CH₂)_(f1)—CO—O— inwhich * represents a binding position to —CO—, and f1 is the same asdefined above, and is more preferably *—O— or *—O—CH₂—CO—O—, and isespecially preferably *—O—.

Each of R^(a4) and R^(a5) is preferably a methyl group.

For R^(a6) and R^(a7), examples of the alkyl group include a methylgroup, an ethyl group, a propyl group, an isopropyl group, a butylgroup, a tert-butyl group, a pentyl group, a heptyl group, a2-ethylheptyl group and an octyl group.

For R^(a6) and R^(a7), examples of the alicyclic hydrocarbon groupinclude a monocyclic alicyclic hydrocarbon group such as a cyclohexylgroup, a methylcyclohexyl group, a dimethylcyclohexyl group, acycloheptyl group and a methylcycloheptyl group, and a polycyclicalicyclic hydrocarbon group such as a decahydronaphthyl group, anadamantyl group, a norbornyl group, and a methylnorbornyl group.

For R^(a6) and R^(a7), examples of the group consisting of an alkylgroup and an alicyclic hydrocarbon group include an aralkyl group suchas a benzyl group, and a phenethyl group.

The alkyl group represented by R^(a6) and R^(a7) is preferably a C1-C6alkyl group, more preferably a methyl group, an ethyl group or anisopropyl group, and still more preferably an ethyl group, or anisopropyl group.

The alicyclic hydrocarbon group represented by R^(a6) and R^(a7) ispreferably a C3-C8 alicyclic hydrocarbon group, more preferably a C3-C6alicyclic hydrocarbon group.

The “m1” is preferably an integer of 0 to 3, and is more preferably 0 or1.

The “n1” is preferably an integer of 0 to 3, and is more preferably 0 or1.

The “n1′” is preferably 0 or 1.

Examples of the structural unit (a1-0) include those represented byformulae (a1-0-1) to (a1-0-12), preferably those represented by formulae(a1-0-1) to (a1-0-10).

Examples of the structural unit (a1-0) further include such groups thata methyl group corresponding to R^(a01) has been replaced by a hydrogenatom in any one of formulae (a1-0-1) to (a1-0-12).

Examples of the monomer from which the structural unit (a1-1) is derivedinclude the monomers described in JP2010-204646A1, and the followingmonomers represented by the formulae (a1-1-1) to (a1-1-4) and suchgroups that a methyl group has been replaced by a hydrogen atom in anyone of formulae (a1-1-1) to (a1-1-4), preferably the following monomersrepresented by the formulae (a1-1-1) to (a1-1-4).

Preferred examples of the structural unit (a1-2) include onesrepresented by formulae (a1-2-1) to (a1-2-6) and those represented bythe formulae in which a methyl group corresponding to R^(a5) has beenreplaced by a hydrogen atom, more preferably the monomers represented byformulae (a1-2-2), (a1-2-5) and (a1-2-6).

When the resin comprises one or more of the structural units representedby formulae (a1-0), (a1-1) and (a1-2), the total content of thestructural units is usually 10 to 95% by mole, preferably 15 to 90% bymole and more preferably 20 to 85% by mole, still more preferably 25 to70% by mole, and further more preferably 30 to 65% by mole, based on100% by mole of all the structural units of the resin.

Examples of the structural unit (a1) having the group represented byformula (2) include a structural unit represented by formula (a1-4). Thestructural unit is sometimes referred to as “structural unit (a1-4)”.

In the formula, R^(a32) represents a hydrogen atom, a halogen atom or aC1-C6 alkyl group that may have a halogen atom,

R^(a33) in each occurrence independently represent a halogen atom, ahydroxy group, a C1-C6 alkyl group, a C1-C6 alkoxy group, a C2-C4 acylgroup, a C2-C4 acyloxy group, an acryloyloxy group or methacryloyloxygroup,

“la” represents an integer 0 to 4,

R^(a34) and R^(a35) each independently represent a hydrogen atom or aC1-C12 hydrocarbon group; and

R^(a36) represents a C1-C20 hydrocarbon group, or R^(a35) and R^(a36)may be bonded together with a C—O bonded thereto to form a divalentC3-C20 heterocyclic group, and a methylene group contained in thehydrocarbon group or the divalent heterocyclic group may be replaced byan oxygen atom or a sulfur atom.

Examples of the alkyl group of R^(a32) and R^(a33) include methyl,ethyl, propyl, isopropyl, butyl, pentyl and hexyl groups. The alkylgroup is preferably a C1-C4 alkyl group, and more preferably a methylgroup or an ethyl group, and still more preferably a methyl group.

Examples of the halogen atom of R^(a32) and R^(a33) include a fluorine,chlorine, bromine and iodine atoms.

Examples of the alkyl group that may have a halogen atom includetrifluoromethyl, difluoromethyl, methyl, perfluoroethyl,2,2,2-trifluoroethyl, 1,1,2,2-tetrafluoroethyl, ethyl, perfluoropropyl,2,2,3,3,3-pentafluoropropyl, propyl, perfluorobutyl,1,1,2,2,3,3,4,4-octafluorobutyl, butyl, perfluoropentyl,2,2,3,3,4,4,5,5,5-nonafluoropentyl, n-pentyl, n-hexyl andn-perfluorohexyl groups.

Examples of an alkoxy group include methoxy, ethoxy, propoxy, butoxy,pentyloxy and hexyloxy groups. The alkoxy group is preferably a C1-C4alkoxy group, more preferably a methoxy group or an ethoxy group, andstill more preferably a methoxy group.

Examples of the acyl group include acetyl, propionyl and butyryl groups.Examples of the acyloxy group include acetyloxy, propionyloxy andbutyryloxy groups. Examples of the hydrocarbon group for R^(a34) andR^(a35) are the same examples as described in R^(a1′) and R^(a2′) in theformula (2).

Examples of hydrocarbon group for R^(a36) include a C1-C20 alkyl group,a C3-C18 alicyclic hydrocarbon group, a C6-C18 aromatic hydrocarbongroup or a group formed by combining thereof.

Examples of an alkyl group for R^(a36) include methyl, ethyl, propyl,isopropyl, butyl, pentyl, hexyl, octyl, decyl, and dodecyl groups.Examples of an alicyclic hydrocarbon group for R^(a36) include a C3-C18cycloalkyl groups such as a cyclopropyl group, a cyclohexyl group, and acyclooctyl group.

Examples of an aromatic hydrocarbon group for R^(a36) include a phenylgroup, a naphthyl group, an anthryl group, a biphenyl group, and aphenanthryl group.

In the formula (a1-4), R^(a32) is preferably a hydrogen atom.

R^(a33) is preferably a C1-C4 alkoxy group, more preferably a methoxygroup or an ethoxy group, and still more preferably a methoxy group.“la” is preferably 0 or 1, and more preferably 0. R^(a34) is preferablya hydrogen atom. R^(a36) is preferably a C1-C12 hydrocarbon group, andmore preferably a methyl group or an ethyl group.

The hydrocarbon group for R^(a36) is preferably a C1-C18 alkyl group, aC3-C18 alicyclic hydrocarbon group, a C6-C18 aromatic hydrocarbon groupor a combination thereof, and more preferably a C1-C18 alkyl group, aC3-C18 alicyclic hydrocarbon group or a C7-C18 aralkyl group. The alkylgroup and the alicyclic hydrocarbon group for

R^(a36) are preferably unsubstituted. When the aromatic hydrocarbongroup of R^(a36) has a substituent, the substituent is preferably aC6-C10 aryloxy group.

Examples of the structural unit (a1-4) include those derived from themonomers described in JP2010-204646A1. Among them, the structural unitis preferably the following ones represented by formula (a1-4-1) toformula (a1-4-8), and more preferably the structural units representedby formula (a1-4-1) to formula (a1-4-5).

When the resin (A) has the structural unit (a1-4), the proportionthereof is preferably 10% by mole to 95% by mole, more preferably 15% bymole to 90% by mole, still more preferably 20% by mole to 85% by mole,further more preferably 20% by mole to 70% by mole, still further morepreferably 20% by mole to 60% by mole, based on the all the structuralunits of the resin (A) (100% by mole).

Examples of the structural unit having an acid-labile group representedby formula (2) include one represented by formula (a1-5).

In formula (a1-5), R^(a8) represents a hydrogen atom, a halogen atom, ora C1-C6 alkyl group which may have a halogen atom,

Z^(a1) represents a single bond or *—(CH₂)_(h3)—CO-L⁵⁴- in which h3represents an integer of 1 to 4 and * represents a binding position toL⁵¹, L⁵¹, L⁵², L⁵³ and L⁵⁴ each independently represent an oxygen atomor a sulfur atom, and

s1 represents an integer of 1 to 3, and s1′ represents an integer of 0to 3.

Herein, the structural unit represented by formula (a1-5) is sometimesreferred to as “structural unit (a1-5)”.

Examples of halogen atoms include a fluorine atom and chlorine atom,preferably a fluorine atom.

Examples of the alkyl group which may have a halogen atom include amethyl group, an ethyl group, n-propyl group, an isopropyl group,n-butyl group, sec-butyl group, tert-butyl group, a pentyl group, ahexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, afluoromethyl group, and a trifluoromethyl group.

In the formula (a1-5), R^(a8) preferably represents a hydrogen atom, amethyl group, or a trifluoromethyl group.

L⁵¹ represents preferably an oxygen atom.

It is preferred that one of L⁵² and L⁵³ represents an oxygen atom, whilethe other represents a sulfur atom.

s1 preferably represents 1. s1′ represents an integer of 0 to 2.

Z^(a1) preferably represents a single bond or *—CH₂—CO—O— wherein *represents a binding position to L⁵¹.

Examples of the structural unit (a1-5) include one derived from monomermentioned in JP2010-61117A1, which preferably include the followingones.

Among them, the structural units represented by the formula (a1-5-1) and(a1-5-2) are more preferred.

When Resin (A) has a structural unit (a1-5), its content is usually 1 to50% by mole, preferably 3 to 45% by mole and more preferably 5 to 40% bymole, and still more preferably 5 to 30% by mole, based on 100% by moleof all the structural units of the resin.

Another example of the structural unit (a1) further includes thefollowing ones.

When Resin (A) has any one of these structural units, its content isusually 10 to 95% by mole, preferably 15 to 90% by mole, more preferably20 to 85% by mole, still more preferably 20 to 70% by mole, further morepreferably 20 to 60% by mole, based on 100% by mole of all thestructural units of the resin.

The structural unit (s) is derived from a monomer having no acid-labilegroup.

The structural unit (s) preferably has a hydroxy group or a lactonering.

Hereinafter, the structural unit (s) having a hydroxy group is referredto as “structural unit (a2)”, and the structural unit (s) having alactone ring is referred to as “structural unit (a3)”.

The hydroxy group which the structural unit (a2) has may be an alcoholichydroxy group or a phenolic hydroxy group.

When KrF excimer laser (wavelength: 248 nm) lithography system, or ahigh energy laser such as electron beam and extreme ultraviolet is usedas an exposure system, the resin which comprises the structural unit(a2) having a phenolic hydroxy group is preferred. When ArF excimerlaser (wavelength: 193 nm) is used as an exposure system, the resinwhich comprises the structural unit (a2) having an alcoholic hydroxygroup is preferred and the resin which comprises the structural unit(a2-1) described later is more preferred. Resin (A) may have two or moreof the structural units (a2).

Examples of the structural unit (a2) having a phenolic hydroxy groupinclude one represented by formula (a2-A):

In formula (a2-A), R^(a50) represents a hydrogen atom, a halogen atom, aC1-C6 alkyl group or a C1-C6 halogenated alkyl group, A^(a50) representsa single bond or *—X^(a51)-(A^(a52)-X^(a52))_(nb)—, where represents abinding position to the carbon atom bonded to R^(a50), A^(a52)represents a C1-C6 alkanediyl group, X^(a51) and X^(a52) represents —O—,—CO—O—, or —O—CO—, and nb represents an integer of 0 or 1, R^(a51) isindependently in each occurrence a halogen atom, a C1-C6 alkyl group, aC1-C6 alkoxy group, a C2-C4 acyl group, a C2-C4 acyloxy group, anacryloyl group or a methacryloyl group, and mb represents an integer of0 to 4. In the formula (a2-A), examples of the halogen atom include afluorine atom, a chlorine atom, a bromine atom or iodine atom, examplesof the C1-C6 alkyl group include a methyl group, an ethyl group, apropyl group, an isopropyl group, a butyl group, an isobutyl group, asec-butyl group, a tert-butyl group, a pentyl group and a hexyl group,and a C1-C4 alkyl group is preferred and a C1-C2 alkyl group is morepreferred and a methyl group is especially preferred.

Examples of the C1-C6 halogenated alkyl group include a trifluoromethylgroup, a pentafluoroethyl group, a heptafluoropropyl group, aheptafluoroisopropyl group, a nonafluorobutyl group, anonafluoro-sec-butyl group, a nonafluoro-tert-butyl group, aperfluoropentyl group and a perfluorohexyl group.

Examples of the C1-C6 alkoxy group include a methoxy group, an ethoxygroup, a propoxy group, an isopropoxy group, a butoxy group, anisobutoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxygroup and a hexyloxy group, and a C1-C4 alkoxy group is preferred and aC1-C2 alkoxy group is more preferred and a methoxy group is especiallypreferred.

Examples of the C2-C4 acyl group include an acetyl group, a propionylgroup and a butyryl group, and examples of the C2-C4 acyloxy groupinclude an acetyloxy group, a propionyloxy group and a butyryloxy group.

R^(a51) is preferably a methyl group.

R^(a50) is preferably a hydrogen atom and a C1-C4 alkyl group, morepreferably a hydrogen atom, a methyl group and an ethyl group, and stillmore preferably a hydrogen atom and a methyl group.

As to A^(a50), examples of *X^(a51)-(A^(a52)-X^(a52))_(nb)— include*—O—, *—CO—O—, *—O—CO—, *—CO—O-A^(a52)-CO—O—, —O—CO-A^(a52)-O—,—O-A^(a52)-CO—O—, *—CO—O-A^(a52)-O—CO—, —O—CO-A^(a52)-O—CO—, preferably*—CO—O—, CO—O-A5-CO—O— and *—O-A^(a52-)CO—O—.

As to A^(a52), examples of the alkanediyl group include an ethylenegroup, a propane-1,3-diyl group, a propane-1,2-diyl group, abutane-1,4-diyl group, a pentane-1,5-diyl group, a hexane-1,6-diylgroup, a butane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a2-methylbutane-1,4-diyl group.

A^(a50) is preferably a single bond, *—CO—O— or *—CO—O-A^(a52)-O—CO—,more preferably a single bond, *—CO—O— or *—CO—O—CH₂—O—CO—, and stillmore preferably a single bond or *—CO—O—.

In the formula (a2-A), mb is preferably 0, 1 or 2, and is morepreferably 0 or 1, and especially preferably 0.

In formula (a2-A), a hydroxyl group on the phenyl group is positionedpreferably on o-position or p-position, and more preferably onp-position.

Examples of the structural unit (a2) include those derived from themonomers described in JP2010-204634A1 and JP2012-12577A1. Preferredexamples of the structural unit (a2) include the structural unitsrepresented by formulae (a2-2-1) to (a2-2-4) and those represented byformulae in which a methyl group corresponding to R^(a50) has beenreplaced by a hydrogen atom.

Among them, the structural units represented by formulae (a2-2-1) and(a2-2-4) and those represented by formulae in which a methyl groupcorresponding to R^(a50) has been replaced by a hydrogen atom are morepreferred.

When Resin (A) has the structural unit represented by formula (a2-A),its content is usually 5 to 80% by mole and preferably 10 to 70% bymole, more preferably 15 to 65% by mole, and still further morepreferably 20 to 65% by mole, based on the sum of the structural unitsof the resin.

Examples of the structural unit (a2) having an alchoholic hydroxy groupinclude one represented by formula (a2-1):

wherein R^(a14) represents a hydrogen atom or a methyl group, R^(a15)and R^(a16) each independently represent a hydrogen atom, a methyl groupor a hydroxy group, L^(a3) represents *—O— or *—O—(CH₂)_(k2)—CO—O— inwhich * represents a binding position to —CO—, and k2 represents aninteger of 1 to 7, and o1 represents an integer of 0 to 10.

Hereinafter, the structural unit represented by formula (a2-1) isreferred to as “structural unit (a2-1)”

In the formula (a2-1), R^(a14) is preferably a methyl group. R^(a15) ispreferably a hydrogen atom. R^(a16) is preferably a hydrogen atom or ahydroxy group. L^(a3) is preferably *—O— or *—O—(CH₂)_(f2)—CO—O— inwhich * represents a binding position to —CO—, and f2 represents aninteger of 1 to 4, is more preferably *—O— and *—O—CH₂—CO—O—, and isstill more preferably *—O—, and o1 is preferably 0, 1, 2 or 3 and ismore preferably 0 or 1.

Examples of monomers from which the structural unit (a2-1) is derivedinclude compounds as mentioned in JP2010-204646A.

Preferred examples of the structural unit (a2-1) include thoserepresented by formulae (a2-1-1) to (a2-1-6).

Among them, more preferred are the structural units represented byformulae (a2-1-1), (a2-1-2), (a2-1-3) and (a2-1-4), still more preferredare the structural units represented by formulae (a2-1-1) and (a2-1-3).

When Resin (A) has the structural unit (a2-1), its content is usually 1to 45% by mole, preferably 1 to 40% by mole, and more preferably 1 to35% by mole, still more preferably 2 to 20% by mole, further still morepreferably 2 to 10% by mole, based on the sum of the structural units ofthe resin.

Examples of the lactone ring for the structural unit (a3) include amonocyclic lactone ring such as β-propiolactone ring, y-butyrolactonering and y-valerolactone ring, and a condensed ring formed from amonocyclic lactone ring and the other ring. Among them, preferred arey-butyrolactone ring and a condensed lactone ring formed fromy-butyrolactone ring and the other ring.

Preferred examples of the structural unit (a3) include those representedby formulae (a3-1), (a3-2), (a3-3) and (a3-4).

In formulae, L^(a4), L^(a5) and L^(a6) each independently represent *—O—or *—O—(CH₂)_(k3)—CO—O— in which * represents a binding position to acarbonyl group and k3 represents an integer of 1 to 7,

R^(a18), R^(a19) and R^(a20) each independently represent a hydrogenatom or a methyl group,

R^(a21) represents a C1-C4 monovalent aliphatic hydrocarbon group,

R^(a24) represents a hydrogen atom, a halogen atom, or a C1-C6 alkylgroup which may have a halogen atom,

R^(a22), R^(a23) and R^(a25) each independently represent a carboxylgroup, a cyano group, or a C1-C4 aliphatic hydrocarbon group,

L^(a7) represents an oxygen atom, *—O-L^(a8)-O—, * —O-L^(a8)-CO—O—,*¹—O-L^(a8)-CO—O-L^(a9)-CO—O— or *¹—O-L^(a8)-CO—O-L^(a9)-O— in whichL^(a8) and L^(a9) each independently represent C1-C6 divalent alkanediylgroup, * represents a binding position to a carbonyl group,

p1 represents an integer of 0 to 5,

q1 and r1 each independently represent an integer of 0 to 3, and

w1 represents an integer of 0 to 8.

Examples of the aliphatic hydrocarbon group represented by R^(a21),R^(a22), R^(a23) and R^(a25) include alkyl groups such as a methylgroup, an ethyl group, a propyl group, or a butyl group.

Examples of the alkyl group represented by R^(a24) include a methylgroup, an ethyl group, a propyl group, a butyl group, a pentyl group,and a hexyl group, preferably a C1-C4 alkyl group, and more preferably amethyl group and an ethyl group.

Examples of halogen atom represented by R^(a24) include a fluorine atom,a chlorine atom, a bromine atom and an iodine atom.

As to R^(a24), examples of the alkyl group which has an halogen atominclude a trifluoromethyl group, a pentafluoroethyl group, aheptafluoropropyl group, a heptafluoroisopropyl group, a nonafluorobutylgroup, a nonafluoro-sec-butyl group, a nonafluoro-tert-butyl group, aperfluoropentyl group, a perfluorohexyl group, a trichloromethyl group,a tribromomethyl group, and a triiodomethyl group.

As to L^(a8) and L^(a9), examples of the alkanediyl group include amethylene group, an ethylene group, a propane-1,3-diyl group, abutane-1,4-diyl group, a pentane-1,5-diyl group and a hexane-1,6-diylgroup, a butane-1,3-diyl group, 2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group and a2-methylbutane-1,4-diyl group.

Preferably, L^(a4), L^(a5) and L^(a6) each independently represent *—O—or *—O—(CH₂)_(d1)—CO—O— in which * represents a binding position to —CO—and d1 represents an integer of 1 to 4. More preferably, L^(a4), L^(a5)and L^(a6) are *—O— and *—O—CH₂—CO—O—, and still more preferably L^(a4),L^(as) and L^(a6) are *—O—.

R^(a18), R^(a9) and R^(a20) are preferably methyl groups. R^(a21) ispreferably a methyl group. Preferably, R^(a22) and R^(a23) areindependently in each occurrence a carboxyl group, a cyano group or amethyl group.

Preferably, p1, q1 and r1 each independently represent an integer of 0to 2, and more preferably p1, q1 and r1 each independently represent 0or 1.

R^(a24) is preferably a hydrogen atom or a C1-C4 alkyl group, morepreferably a hydrogen atom, a methyl group or an ethyl group, and stillmore preferably a hydrogen atom or a methyl group.

L^(a7) represents preferably an oxygen atom or *1-O-L^(a8)-CO—O—, morepreferably an oxygen atom, *¹—O—CH₂—CO—O— or *—O—C₂H₄—CO—O—.

The formula (a3-4)′ is preferably the following one.

In the formula, R^(a24) and L^(a7) are as defined above, respectively.

Examples of the monomer from which the structural unit (a3) is derivedinclude those mentioned in US2010/203446A1, US2002/098441A1 andUS2013/143157A1.

Examples of the structural unit (a3) include the following ones.

Other examples of the structural unit (a3) include those represented byformulae (a3-1) to (a3-4) in which the methyl group corresponding toR^(a18), R^(a19), R^(a20) and R^(a24) of formulae (a3-1) to (a3-4) hasbeen replaced by a hydrogen atom.

When Resin (A) has the structural unit (a3), its content thereof ispreferably 5 to 70% by mole, and more preferably 10 to 65% by mole andmore preferably 10 to 60% by mole, based on the sum of the structuralunits of the resin.

When Resin (A) has the structural unit (a3-1), (a3-2), (a3-3) or (a3-4),its content thereof is preferably 5 to 60% by mole, and more preferably5 to 50% by mole and more preferably 10 to 50% by mole, based on the sumof the structural units of the resin.

Other examples of the structural unit (s) include a structural unithaving a fluorine atom and a structural unit which has a hydrocarbon notbeing removed therefrom by action of an acid.

Hereinafter, the structural unit (s) having a halogen atom is referredto as “structural unit (a4)”.

Halogen atoms for the structural unit (a4) may be a fluorine atom, achlorine atom, a bromine atom, or an iodine atom. The structural unit(a4) has preferably a fluorine atom.

Examples of the structural unit (a4) include the following one.

In the formula, R⁴¹ represents a hydrogen atom or a methyl group, R⁴²represents a C1-C24 saturated hydrocarbon group having a fluorine atomin which hydrocarbon group a methylene group can be replaced by anoxygen atom or a carbonyl group.

Examples of the saturated hydrocarbon group include C1-C24 chainhydrocarbon group, an alicyclic hydrocarbon group including a monocyclicor polycyclic hydrocarbon group, and any combinations of these groups.

Examples of the chain hydrocarbon group include a methyl group, an ethylgroup, a propyl group, a butyl group, a pentyl group, a hexyl group, aheptyl group, an octyl group, a decyl group, a dodecyl group, apentadecyl group, a hexadecyl group, a heptadecyl group and an octadecylgroup.

Examples of the alicyclic hydrocarbon group include a cyclopentyl group,a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group,decahydronaphthyl group, an adamantyl group, a norbornyl group and thefollowing groups:

Examples of the combinations of these groups include any combination ofan alkyl or alkanediyl group with an alicyclic hydrocarbon group, whichspecifically include -[alkanediyl group]-[alicyclic hydrocarbon group],-[alicyclic hydrocarbon group]-[alkyl group] and -[alkanediylgroup]-[alicyclic hydrocarbon group]-[alkyl group].

Typical examples of the structural unit (a4) include structural unitsrepresented by formulae (a4-0), (a4-1) and (a4-4).

In the formula (a4-0), R^(5a) represents a hydrogen atom or a methylgroup, L^(4a) represents a single bond or a C1-C4 alkanediyl group,L^(3a) represents a C1-C8 perfluoroalkanediyl group, or a C3-C12perfluorocycloalkanediyl group, and R^(6a) represents a hydrogen atom ora fluorine atom.

For L^(4a), examples of the alkanediyl group include a linear alkanediylgroup such as a methylene group, an ethylene group, a propane-1,3-diylgroup, and butane-1,4-diyl group, and a branched alkanediyl group suchas an ethane-1,1-diyl group, a propane-1,2-diyl group, a butane-1,3-diylgroup, a 2-methylpropane-1,3-diyl group and 2-methylpropane-1,2-diylgroup.

Examples of the perfluoroalkanediyl group for L^(3a) includedifluoromethylene, perfluoroethylene, perfluoropropane-1,3-diyl,perfluoropropane-1,2-diyl, perfluoropropane-2,2-diyl,perfluorobutane-1,4-diyl, perfluorobutane-2,2-diyl,perfluorobutane-1,2-diyl, perfluoropentane-1,5-diyl,perfluoropentane-2,2-diyl, perfluoropentane-3,3-diyl,perfluorohexane-1,6-diyl, perfluorohexane-2,2-diyl,perfluorohexane-3,3-diyl, perfluoroheptane-1,7-diyl,perfluoroheptane-2,2-diyl, perfluoroheptane-3,4-diyl,perfluoroheptane-4,4-diyl, perfluorooctan-1,8-diyl,perfluorooctane-2,2-diyl, perfluorooctan-3,3-diyl andperfluorooctane-4,4-diyl groups.

Examples of the perfluorocycloalkanediyl group for L^(3a) includeperfluorocyclohexanediyl, perfluorocyclopentanediyl,perfluorocycloheptanediyl and perfluoroadamantanediyl groups.

L^(3a) is preferably a C1-C6 perfluoroalkanediyl group, more preferablya C1-C3 perfluoroalkanediyl group.

L^(4a) is preferably a single bond, a methylene group or an ethylenegroup, more preferably a single bond or a methylene group.

Examples of the structural unit represented by formula (a4-0) includethe structural units represented by the following formulae and thoserepresented by the following formulae in which a methyl group has beenreplaced by a hydrogen atom.

The structural unit represented by formula (a4-1) is as follows.

In the formula, R^(a41) represents a hydrogen atom or a methyl group;R^(a42) represents a C1-C20 saturated hydrocarbon group which can have asubstituent and in which a methylene group can be replaced by an oxygenatom or a carbonyl group, provided that each or both of A^(a41) andR^(a42) have a fluorine atom; and

A^(a41) represents a C1-C6 alkanediyl group which may have a substituentor a moiety represented by formula (a-g1):

in which s represents an integer of 0 to 1,

A^(a42) and A^(a44) respectively represent a C1-C5 saturated hydrocarbongroup which may have a substituent,

A^(a43) represents a single bond or a C1-C5 chain or alicyclichydrocarbon group which may have a substituent,

X^(a41) and X^(a42) respectively represent —O—, —CO—, —CO—O—, or —O—CO—,provided that the sum of carbon atoms of A^(a42), A^(a43), A^(a44),X^(a41) and X^(a42) are each 7 or less,

A^(a44) is bonded to —O—CO—R^(a42); and

two of symbols * represent a binding position.

The saturated hydrocarbon group for R^(a42) includes a chain saturatedhydrocarbon group, an alicyclic hydrocarbon group including a monocyclichydrocarbon group and a polycyclic hydrocarbon group, and anycombination of these hydrocarbon groups.

Examples of the chain saturated hydrocarbon group include a methylgroup, an ethyl group, a propyl group, a butyl group, a pentyl group, ahexyl group, a heptyl group, an octyl group, a decyl group, a dodecylgroup, a hexadecyl group, a pentadecyl group, a hexyldecyl group, aheptadecyl group and an octadecyl group.

Examples of alicyclic hydrocarbon groups include cycloalkyl groups suchas a cyclopentyl group, a cyclohexyl group, a cycloheptyl group and acyclooctyl group; and monovalent polycyclic hydrocarbon groups such as adecahydronaphthyl group, an adamantyl group, a norbornyl group, and thefollowing groups where * represents a binding position.

Examples of the combination of these groups include combination of analkanediyl or alkyl group with an alicyclic hydrocarbon group such as-[alkanediyl group]-[alicyclic hydrocarbon group], -[alicyclichydrocarbon group]-[alkyl group], and -[alkanediyl group]-[alicyclichydrocarbon group]-[alkyl group].

The hydrocarbon group represented by R^(a42) preferably has asubstituent.

Examples of the substituent include a halogen atom and a grouprepresented by formula (a-g3):

—X^(a43)-A^(a45)  (a-g3)

in which X^(a43) represents an oxygen atom, a carbonyl group, acarbonyloxy group or an oxycarbonyl group, and

A^(a45) represents a C1-C17 chain or alicyclic hydrocarbon group whichmay have a fluorine atom.

Examples of the chain or alicyclic hydrocarbon group for A^(a45) includealkyl groups such as a methyl group, an ethyl group, a propyl group, abutyl group, a pentyl group, a hexyl group, a heptyl group, an octylgroup, a decyl group, a dodecyl group, a hexadecyl group, a pentadecylgroup, a hexyldecyl group, a heptadecyl group and an octadecyl group;

monocyclic alicyclic hydrocarbon groups such as a cyclopentyl group, acyclohexyl group, a cycloheptyl group and a cyclooctyl group; andmonovalent polycyclic hydrocarbon groups such as a decahydronaphthylgroup, an adamantyl group, a norbornyl group, and the following groupswhere * represents a binding position.

R^(a42) is preferably a chain or alicyclic hydrocarbon group which mayhave a halogen atom, more preferably an alkyl group which has a halogenatom or a group represented by formula (a-g3).

If R^(a42) is a chain or alicyclic hydrocarbon group which has a halogenatom, it is preferably a chain or alicyclic hydrocarbon group which hasa fluorine atom, more preferably a perfluoroalkyl group or aperfluorocycloalkyl group, and still more preferably a C1-C6, especiallyC1-C3, perfluoroalkyl group.

Specific examples of the perfluoroalkyl group include a perfluoromethylgroup, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutylgroup, a perfluoropentyl group, a perfluorohexyl group, aperfluoroheptyl group, and a perfluorooctyl group. Specific examples ofthe perfluorocycloalkyl group include a perfluorocyclohexyl group.

Examples of the substituents for R^(a42) include a hydroxy group, aC1-C6 alkoxy group, and a halogen atom such as a fluorine atom.

If R^(a42) is a chain or alicyclic hydrocarbon group which has a grouprepresented by formula (a-g3), R^(a42) has preferably 15 or less carbonatoms, more preferably 12 or less carbon atoms.

If R^(a42) has a group represented by formula (a-g3), R^(a42) haspreferably one group represented by formula (a-g3).

The chain or alicyclic hydrocarbon group which has a group representedby formula (a-g3) is preferably a group represented by formula (a-g2):

-A^(a46)-X^(a44)-A^(a47)  (a-g2)

in which A^(a46) represents a C1-C17 chain or alicyclic hydrocarbongroup which may have a fluorine atom, X^(a44) represents a carbonyloxygroup or an oxycarbonyl group, and A^(a47) represents a C1-C17 chain oralicyclic hydrocarbon group which may have a fluorine atom, providedthat A^(a46), A^(a47) and X^(a44) have 18 or less of carbon atoms intotal and one or both of A^(a46) and A^(a47) have a fluorine atom.

The chain or alicyclic hydrocarbon group represented by A⁴⁶ haspreferably 1 to 6, more preferably 1 to 3 carbon atoms.

The chain or alicyclic hydrocarbon group represented by A^(a47) haspreferably 4 to 15, more preferably 5 to 12 carbon atoms. A⁴⁷ is morepreferably a cyclohexyl group or an adamantyl group.

Examples of the moiety represented by -A^(a46)-X^(a44)-A^(a47) includethe following ones.

In each formula, * represents a binding position to a carboxy group.

Examples of A^(a41) typically include a C1-C6 alkanediyl group which maybe a linear chain or branched chain. Specific examples of them includelinear chain alkanediyl groups such as a methylene group, an ethylenegroup, a propane-1,3-diyl group, a butane-1,4-diyl group, apentane-1,5-diyl group, or a hexane-1,6-diyl group; and branched chainalkanediyl groups such as a propane-1,3-diyl group, a butane-1,3-diylgroup, a 1-methylbutane-1,2-diyl group, or a 2-methylbutane-1,4-diylgroup. Examples of the substituents on the alkanediyl group include ahydroxy group or a C1-C6 alkoxy group.

A^(a41) is preferably a C1-C4 alkanediyl group, more preferably a C2-C4alkanediyl group, and still more preferably an ethylene group.

Examples of the alkanediyl group represented by A^(a42), A^(a43) andA^(a44) include a methylene group, an ethylene group, a propane-1,3-diylgroup, a butane-1,4-diyl group, a 2-methylpropane-1,3-diyl group, or a2-methylbutane-1,4-diyl group. Examples of the substituents on thealkanediyl group include a hydroxy group or a C1-C6 alkoxy group.

X^(a42) represents an oxygen atom, a carbonyl group, a carbonyloxy groupor an oxycarbonyl group.

Examples of the moiety represented by formula (a-g1) where X^(a42) is anoxygen atom, a carbonyl group, a carbonyloxy group or an oxycarbonylgroup include the following ones:

in which * and ** represent binding positions, and ** represents abinding position to —O—CO—R^(a42).

Typical examples of the structural unit represented by formula (a4-1)include the structural units represented by the following formulae andthose represented by the following formulae in which a methyl groupcorresponding to R^(a41) has been replaced by a hydrogen atom.

Specific examples of the structural unit (a4-1) include a structuralunit represented by the formula (a4-2):

wherein R^(f5) represents a hydrogen atom or a methyl group,

L⁴⁴ represent a C1-C6 alkanediyl group in which a methylene group can bereplaced by —O— or —CO—, and

R^(f6) represents a C1-C20 saturated hydrocarbon group that has afluorine atom, provided that L⁴⁴ and R^(f6) have 2 to 21 carbon atoms intotal.

Examples of the divalent saturated hydrocarbon group for L⁴⁴ include alinear alkanediyl group such as methylene, ethylene, propane-1,3-diyl,propane-1,2-diyl, butane-1,4-diyl, pentane-1,5-diyl and hexane-1,6-diylgroups; and a branched alkanediyl group such as1-methylpropane-1,3-diyl, 2-methylpropane-1,3-diyl,2-methylpropane-1,2-diyl, 1-methylbutane-1,4-diyl and2-methylbutane-1,4-diyl groups.

Examples of the saturated hydrocarbon group for R^(f6) include analiphatic hydrocarbon group and an aromatic hydrocarbon group.

The aliphatic hydrocarbon group includes chain and cyclic groups, and acombination thereof. The aliphatic hydrocarbon group is preferably analkyl group and a cyclic aliphatic hydrocarbon group.

Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl,n-butyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl and2-ethylhexyl groups.

Examples of the cyclic aliphatic hydrocarbon group include any of amonocyclic group and a polycyclic group. Examples of the monocyclicalicyclic hydrocarbon group include a cycloalkyl group such ascyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, methylcyclohexyl,dimethylcyclohexyl, cycloheptyl, cyclooctyl, and cyclodecyl groups.Examples of the polycyclic hydrocarbon groups include decahydronaphthyl,adamantyl, 2-alkyladamantane-2-yl, 1-(adamantane-1-yl)alkane-1-yl,norbornyl, methylnorbornyl and isobornyl groups.

Examples of the saturated hydrocarbon group having a fluorine atom forR^(f6) include an alkyl group having a fluorine atom and an alicyclichydrocarbon group having a fluorine atom.

Specific examples of an alkyl group having a fluorine atom include afluorinated alkyl group such as difluoromethyl, trifluoromethyl,1,1-difluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl,perfluoroethyl, 1,1,2,2-tetrafluoropropyl, 1,1,2,2,3,3-hexafluoropropyl,perfluoroethylmethyl, 1-(trifluoromethyl)-1,2,2,2-tetrafluoroethyl,perfluoropropyl, 1-(trifluoromethyl)-2,2,2-trifluoroethyl,1,1,2,2-tetrafluorobutyl, 1,1,2,2,3,3-hexafluorobutyl,1,1,2,2,3,3,4,4-octafluorobutyl, perfluorobutyl,1,1-bis(trifluoro)methyl-2,2,2-trifluoroethyl, 2-(perfluoropropyl)ethyl,1,1,2,2,3,3,4,4-octafluoropentyl, perfluoropentyl,1,1,2,2,3,3,4,4,5,5-decafluoropentyl,1,1-bis(trifluoromethyl)-2,2,3,3,3-pentafluoropropyl,2-(perfluorobutyl)ethyl, 1,1,2,2,3,3,4,4,5,5-decafluorohexyl,1,1,2,2,3,3,4,4,5,5,6,6-dodecafluorohexyl, perfluoropentylmethyl andperfluorohexyl groups.

Examples of the alicyclic hydrocarbon group having a fluorine atominclude a fluorinated cycloalkyl group such as perfluorocyclohexyl andperfluoroadamantyl groups.

In the formula (a4-2), L⁴⁴ is preferably a C2-C4 alkanediyl group, andmore preferably an ethylene group.

R^(f6) is preferably a C1-C6 fluorinated alkyl group.

Examples of the structural unit represented by formula (a4-2) includeones represented by the formulae (a4-1-1) to (a4-1-11) and those inwhich a methyl group corresponding to R^(f5) has been replaced by ahydrogen atom.

Specific examples of the structural unit (a4-1) include a structuralunit represented by the formula (a4-3).

In formula, R^(f7) represents a hydrogen atom or a methyl group.

L⁵ represents a C1-C6 alkanediyl group.

A^(f13) represents a C1-C18 saturated hydrocarbon group which may have afluorine atom.

X^(f12) represents a carbonyloxy group or an oxycarbonyl group.

A^(f14) represents a C1-C17 saturated hydrocarbon group which may have afluorine atom, provided that one or both of A^(f13) and A^(f14)represents a fluorine-containing aliphatic hydrocarbon group.

Examples of the alkanediyl group for L⁵ include the same ones as thosefor L^(4a).

A^(f13) further includes combined groups of chain hydrocarbon groups andalicyclic hydrocarbon groups.

As to A^(f13), the chain or alicyclic hydrocarbon group which may have afluorine atom is preferably a divalent saturated chain hydrocarbon groupwhich may have a fluorine atom, more preferably a perfluoroalkanediylgroup.

Examples of the divalent chain saturated hydrocarbon group which mayhave a fluorine atom include an alkanediyl group such as a methylenegroup, an ethylene group, a propanediyl group, a butanediyl group andpentanediyl group; and a perfluoroalkanediyl group such as adifluoromethylene group, a perfluoroethylene group, aperfluoropropanediyl group, a perfluorobutanediyl group andperfluoropentanediyl group.

The divalent cyclic saturated hydrocarbon group which may have afluorine atom may be a divalent monocyclic or polycyclic group.

Examples of the divalent monocyclic hydrocarbon group which may have afluorine atom include a cyclohexanediyl group and aperfluorocyclohexanediyl group.

Examples of the divalent polycyclic hydrocarbon group which may have afluorine atom include an adamantanediyl group, norbornanediyl group, anda perfluoroadamantanediyl group.

In the group represented by A^(f14), the aliphatic hydrocarbon groupincludes chain saturated hydrocarbon groups, cyclic saturatedhydrocarbon groups and combined groups of these saturated hydrocarbongroups.

As to A^(f14), the chain or alicyclic hydrocarbon group which may have afluorine atom is preferably a saturated aliphatic hydrocarbon groupwhichmayhave a fluorine atom, more preferablyaperfluoroalkyl group.

Examples of the chain hydrocarbon group which may have a fluorine atominclude a trifluoromethyl group, a fluoromethyl group, a methyl group, aperfluoroethyl group, a 1,1,1-trifluoroethyl group, a1,1,2,2-tetrafluoroethyl group, an ethyl group, a perfluoropropyl group,a 1,1,1,2,2-pentafluoropropyl group, a propyl group, a perfluorobutylgroup, 1,1,2,2,3,3,4,4-octafluorobutyl group, a butyl group, aperfluoropentyl group, 1,1,1,2,2,3,3,4,4-nonafluoropentyl group, apentyl group, a hexyl group, a perfluorohexyl group, a heptyl group, aperfluoroheptyl group, an octyl group and a perfluorooctyl group.

The alicyclic hydrocarbon group which may have a fluorine atom may bemonocyclic or polycyclic group.

Examples of the monovalent monocyclic hydrocarbon group which may have afluorine atom include a cyclopropyl group, a cyclopentyl group, acyclohexyl group, and a perfluorocyclohexyl group.

Examples of the polycyclic hydrocarbon group which may have a fluorineatom include an adamantyl group, a norbornyl group, and aperfluoroadamantyl group.

Examples of the combined groups of the above-mentioned chain andalicyclic hydrocarbon groups include a cyclopropylmethyl group, acyclobutylmethyl group, an adamantylmethyl group, a norbornylmethylgroup and a perfluoroadamantylmethyl group.

In formula (a4-3), L⁵ is preferably an ethylene group.

The chain or alicyclic hydrocarbon group represented by A^(f13) haspreferably 6 or less, more preferably 2 to 3, carbon atoms.

The chain or alicyclic hydrocarbon group represented by A^(f14) haspreferably 3 to 12, more preferably 3 to 10, carbon atoms.

A^(f14) has preferably a C3-C12 alicyclic hydrocarbon group, morepreferably a cyclopropylmethyl group, a cyclopentyl group, a cyclohexylgroup, a norbornyl group or an adamantyl group.

Examples of the structural unit represented by formula (a4-3) includepreferably those represented by the he formulae (a4-1′-1) to (a4-1′-11)and those in which a methyl group corresponding to R^(f7) has beenreplaced by a hydrogen atom.

The structural unit represented by formula (a4-4) is as follows.

In formula (a4-4), R^(f21) represents a hydrogen atom or a methyl group;

A^(f21) represents —(CH₂)_(j1)—, —(CH₂)_(j2)—O—(CH₂)_(j3)— or—(CH₂)_(j4)—CO—O—(CH₂)_(j5)— where j1, j2, j3, j4 or j5 eachindependently represent an integer of 1 to 6; and

R^(f22) represents a C1-C10 hydrocarbon group having a fluorine atom.

R^(f22) is preferably a C1-C10 alkyl group having a fluorine atom or aC3-C10 alicyclic hydrocarbon group having a fluorine atom, morepreferably a C1-C10 alkyl group having a fluorine atom, and still morepreferably a C1-C6 alkyl group having a fluorine atom.

In formula (a4-4), A^(f21) is preferably —(CH₂)_(j1)—, more preferably amethylene or ethylene group, and still more preferably a methylenegroup.

Examples of the structural unit represented by formula (a4-4) includepreferably the following ones and those represented by the followingformulae in which the methyl group corresponding to R^(f21) has beenreplaced by a hydrogen atom.

When Resin (A) has the structural unit (a4), its content is preferably 1to 20% by mole, more preferably 2 to 15% by mole and still morepreferably 3 to 10% by mole based on 100% by mole of all the structuralunits of the resin.

Other examples of the structural unit (s) include one having anacid-stable hydrocarbon group. The structural unit (s) having anacid-stable hydrocarbon group is sometimes referred to as “structuralunit (a5)”.

Herein, the term “acid-stable hydrocarbon group” means such ahydrocarbon group that is not removed from the structural unit havingthe group by action of an acid generated from an acid generator asdescribed above.

The acid-stable hydrocarbon group may be a linear, branched or cyclichydrocarbon group.

The structural unit which has a hydrocarbon not being removed therefromby action of an acid may have a linear, branched or cyclic hydrocarbon,preferably an alicyclic hydrocarbon group.

Examples of the structural unit having an acid-stable hydrocarbon groupinclude one represented by formula (a5-1):

where R⁵¹ represents a hydrogen atom or a methyl group;

R⁵² represents a C3-C18 monovalent alicyclic hydrocarbon group which mayhave a C1-C8 monovalent aliphatic hydrocarbon group as a substituent,provided that the alicyclic hydrocarbon group has no substituent on thecarbon atom bonded to L⁵⁵; and

L⁵⁵ represents a single bond or a C1-C18 divalent saturated hydrocarbongroup where a methylene group can be replaced by an oxygen atom orcarbonyl group.

The alicyclic hydrocarbon group represented by R⁵² may be a monocyclicor a polycyclic one.

Examples of the alicyclic hydrocarbon group include a monocyclichydrocarbon group such as a C3-C18 cycloalkyl group (e.g. a cyclopropylgroup, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group) anda polycyclic alicyclic hydrocarbon group such as an adamantyl group, ora norbornyl group.

Examples of the aliphatic hydrocarbon group include an alkyl groups suchas a methyl group, an ethyl group, n-propyl group, isopropyl group,n-butyl group, sec-butyl group, tert-butyl group, a pentyl group, ahexyl group, an octyl group and 2-ethylhexyl group.

Examples of the alicyclic hydrocarbon group having a substituent includea 3-hydroxyadamantyl group, and a 3-methyladamantyl group.

R⁵² is preferably a C3-C18 unsubstituted alicyclic hydrocarbon group,more preferably an adamantyl group, a norbornyl group or a cyclohexylgroup.

Examples of the divalent saturated hydrocarbon group represented by L⁵⁵include divalent aliphatic hydrocarbon groups and divalent alicyclichydrocarbon groups, preferably divalent aliphatic hydrocarbon groups.

Examples of divalent aliphatic hydrocarbon groups include alkanediylgroups such as a methylene group, an ethylene group, a propanediylgroup, a butanediyl group and a pentanediyl group.

The divalent alicyclic hydrocarbon groups may be monocyclic orpolycyclic one.

Examples of divalent monocyclic hydrocarbon groups includecycloalkanediyl groups such as a cyclopentanediyl group and acyclohexanediyl group. Examples of divalent polycyclic alicyclichydrocarbon groups include an adamantanediyl group and a norbornanediylgroup.

Examples of the divalent hydrocarbon group where a methylene group hasbeen replaced by an oxygen atom or carbonyl group include thoserepresented by formulae (L1-1) to (L1-4).

In these formulae, * represents a binding position to an oxygen atom.

X^(x1) is a carbonyloxy group or an oxycarbonyl group; and

L^(x1) is a C1-C16 divalent aliphatic saturated hydrocarbon group, andL^(x2) is a single bond or a C1-C15 divalent chain or alicyclichydrocarbon group, provided that the total number of the carbon atoms inL^(x1) and L^(x2) is 16 or less.

L^(x3) is a C1-C17 divalent aliphatic saturated hydrocarbon group, andL^(x4) is a single bond or a C1-C16 divalent chain or alicyclichydrocarbon group, provided that the total number of the carbon atoms inL^(x3) and L^(x4) is 17 or less.

L^(x5) is a C1-C15 divalent aliphatic saturated hydrocarbon group, andL⁶ and L^(x7) are a single bond or a C1-C14 divalent chain or alicyclichydrocarbon group, provided that the total number of the carbon atoms inL^(x5), L^(x6) and L^(x7) is 15 or less.

L^(x8) and L^(x9) are each independently a single bond or a C1-C12divalent chain or alicyclic hydrocarbon group, and W^(x1) is a C3-C15divalent cyclic saturated hydrocarbon group, provided that the totalnumber of the carbon atoms in L^(x8), L^(x9) and W^(x1) is 15 or less.

L^(x1) is preferably a C1-C8 divalent aliphatic saturated hydrocarbongroup, more preferably a methylene group or an ethylene group.

L² is preferably a single bond, or a C1-C8 divalent aliphatic saturatedhydrocarbon group, more preferably a single bond.

L^(x3) is preferably a C1-C8 divalent aliphatic saturated hydrocarbongroup, more preferably a methylene group or an ethylene group.

L^(x4) is preferably a single bond or a C1-C8 divalent aliphaticsaturated hydrocarbon group, more preferably a single bond, a methylenegroup or an ethylene group.

L^(x5) is preferably a C1-C8 divalent aliphatic saturated hydrocarbongroup, more preferably a methylene group or an ethylene group.

L^(x6) is preferably a single bond or a C1-C8 divalent aliphaticsaturated hydrocarbon group, more preferably a methylene group or anethylene group.

L^(x7) is preferably a single bond or a C1-C8 divalent aliphaticsaturated hydrocarbon group, more preferably a methylene group or anethylene group.

L^(x8) is preferably a single bond or a C1-C8 divalent aliphaticsaturated hydrocarbon group, more preferably a single bond or amethylene group.

L^(x9) is preferably a single bond or a C1-C8 divalent aliphaticsaturated hydrocarbon group, more preferably a single bond or amethylene group.

W^(x1) is a preferably C3-C10 divalent cyclic saturated hydrocarbongroup, more preferably a cyclohexanediyl group or an adamantanediylgroup.

Examples of the group represented by formula (L1-1) include thefollowing ones.

In these formulae, * represents a binding position to an oxygen atom.

Examples of the group represented by formula (L1-2) include thefollowing ones.

In these formulae, * represents a binding position to an oxygen atom.

Examples of the group represented by formula (L1-3) include thefollowing ones.

In these formulae, * represents a binding position to an oxygen atom.

Examples of the group represented by formula (L1-4) include thefollowing ones.

In these formulae, * represents a binding position to an oxygen atom.

L⁵⁵ is preferably a single bond or a group represented by formula(L1-1).

Examples of the structural unit represented by formula (a5-1) includethe following ones and those where a methyl group has been replaced by ahydrogen atom in each formula.

When Resin (A) has the structural unit (a5), its content is preferably 1to 30% by mole, more preferably 2 to 20% by mole and still morepreferably 3 to 15% by mole based on 100% by mole of all the structuralunits of the resin.

<Structural Unit (II)>

Resin (A) may comprise a structural unit decomposed by irradiation togenerate an acid. Said structural unit is referred to as “the structuralunit (II)”. Examples of the structural unit (II) include one asdescribed in JP2016-79235A1.

The structural unit (II) preferably comprises a sulfonate or carboxylategroup and an organic cation, or a S⁺ group and an organic anion at itsside chain.

The structural unit (II) which comprises a sulfonate or carboxylategroup and an organic cation at its side chain is preferably representedby formula (II-2-A′):

wherein X^(III3) represents a C1-C18 divalent saturated hydrocarbongroup in which a methylene group can be replaced by —O—, —S— or —CO— andin which a hydrogen atom can be replaced by a fluorine atom, a hydroxylgroup or a C1-C6 alkyl group which may have a fluorine atom,

A^(x1) represents a C1-C8 alkanediyl group in which a hydrogen atom canbe replaced by a fluorine atom or a C1-C6 perfluoroalkyl group, RA⁻represents a sulfonate or carboxylate group,

R^(III3) represents a hydrogen atom, a halogen atom or a C1-C6 alkylgroup in which a hydrogen atom can be replaced by a halogen atom, andZA⁺ represents an organic cation.

For R^(III3), examples of the halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom.

For R^(III3), examples of a halogen-containing alkyl group include aperfluoromethyl group and a perfluoroethyl group.

For A^(X1), examples of the alkanediyl group include a methylene group,an ethylene group, a propane-1,3-diyl group, a butane-1,4-diyl group, apentane-1,5-diyl group, a hexane-1,6-diyl group, an ethane-1,1-diylgroup, a propane-1,1-diyl group, a propane-1,2-diyl group, apropane-2,2-diyl group, a pentane-2,4-diyl group, a2-methylpropane-1,3-diyl group, 2-methylpropane-1,2-diyl group,pentane-1,4-diyl group, and 2-methylbutane-1,4-diyl group.

For X^(III3), examples of divalent aliphatic hydrocarbon groups includea linear alkanediyl group, a branched alkanediyl group, a monocyclicalicyclic hydrocarbon, a polycyclic alicyclic hydrocarbon, and anycombinations of these groups, specific examples of which include alinear alkanediyl group such as a methylene group, an ethylene group, apropane-1,3-diyl group, a propane-1,2-diyl group, a butane-1,4-diylgroup, a pentane-1,5-diyl group, a hexane-1,6-diyl group, aheptane-1,7-diyl group, an octane-1,8-diyl group, a nonane-1,9-diylgroup, a decane-1,10-diyl group, an undecane-1,11-diyl group, adodecane-1,12-diyl group; a branched alkanediyl group such as abutane-1,3-diyl group, a 2-methylpropane-1,3-diyl group, a2-methylpropane-1,2-diyl group, a pentane-1,4-diyl group, and a2-methylbutane-1,4-diyl group; cycloalkanediyl groups such as acyclobutane-1,3-diyl group, a cyclopentane-1,3-diyl group, acyclohexane-1,4-diyl group and a cyclooctane-1,5-diyl group; anddivalent polycyclic alicyclic hydrocarbon groups such asnorbornane-1,4-diyl group, norbornane-2,5-diyl group,adamantane-1,5-diyl group, and adamantane-2,6-diyl group.

Examples of the saturated hydrocarbon group in which a methylene grouphas been replaced by —O—, —S— or —CO— include divalent groupsrepresented by the formulae (X1) to (X53).

In each formula, X³ represents a C1-C16 divalent hydrocarbon group, X⁴represents a C1-C15 divalent hydrocarbon group, X⁵ represents a C1-C13divalent hydrocarbon group, X⁶ represents a C1-C14 divalent hydrocarbongroup, X⁷ represents a C1-C14 divalent hydrocarbon group, and X⁸represents a C1-C13 divalent hydrocarbon group and * represents abinding position to A^(x1), provided that each divalent grouprepresented by one of formulae (X1) to (X53) has 1 to 17 carbon atoms intotal.

Examples of the organic cation represented by ZA⁺ include an organiconium cation such as an organic sulfonium cation, an organic iodoniumcation, an organic ammonium cation, a benzothiazolium cation and anorganic phosphonium cation.

Among them, an organic sulfonium cation and an organic iodonium cationare preferred, and a sulfonium cation, specifically an arylsulfoniumcation, is more preferred.

The structural unit represented by formula (II-2-A′) is preferablyrepresented by formula (II-2-A):

wherein X^(III3), R^(III3) and ZA⁺ are as defined above;

R^(III2) and R^(III4) each independently represent a hydrogen atom, afluorine atom or a C1-C6 perfluoroalkyl group;

z represents an integer of 0 to 6; and

Q^(a) and Q^(b) each independently represent a fluorine atom or a C1-C6perfluoroalkyl group.

For Q^(a), Q^(b), R^(III2) and R^(III4), examples of a perfluoroalkylgroup include a trifluoromethyl group, a pentafluoroethyl group, aheptafluoropropyl group, a nonafluorobutyl group, an undecafluoropentylgroup and a tridecafluorohexyl group, and a trifluoromethyl group ispreferred.

The structural unit represented by formula (II-2-A) is preferablyrepresented by formula (II-2-A-1):

wherein R^(III2), R^(III3), R^(III4), Q^(a), Q^(b), z and ZA⁺ are asdefined above; R^(III5) represents a C1-C12 saturated hydrocarbon group,and X^(I2) represents a C1-C18 divalent saturated hydrocarbon group inwhich a methylene group can be replaced by —O—, —S— or —CO— and in whicha hydrogen atom can be replaced by a halogen atom or a hydroxyl group.

For R^(III5), examples of the saturated hydrocarbon group include chainalkyl groups such as methyl group, an ethyl group, a propyl group, anisopropyl group, a butyl group, a sec-butyl group, a tert-butyl group, apentyl group, a hexyl group, a heptyl group, a 2-ethylhexyl group and adodecyl group.

For X^(I2), examples of the divalent saturated hydrocarbon group includethe same examples as the divalent saturated hydrocarbon group forX^(III3).

The structural unit represented by formula (II-2-A-1) is preferablyrepresented by formula (II-2-A-2):

wherein R^(III3), R^(III5), and ZA⁺ are as defined above; and n and meach independently represent 1 or 2.

Examples of the structural unit represented by formula (II-2-A′) includethe following ones and those recited in WO2012/050015A1.

The structural unit (II) which comprises a S⁺ group and an organic anionat its side chain is preferably represented by formula (II-1-1):

wherein A^(II1) represents a single bond or a divalent connecting group,R^(II) represents a C6-C18 divalent aromatic hydrocarbon group, R^(II2)and R^(II3) each independently represent a C1-C18 hydrocarbon group orjointly represents a ring structure together S⁺ bonded thereto, R^(II4)represents a hydrogen atom, a halogen atom or a C1-C6 alkyl group inwhich a hydrogen atom can be replaced by a halogen atom, and A⁻represents an organic anion.

For R^(II1), examples of the aromatic hydrocarbon group include aphenylene group and naphthylene group.

For R^(II2) and R^(II3), examples of the hydrocarbon group include thealkyl groups, alicyclic hydrocarbon groups, aromatic hydrocarbon groupsand any combination of these groups.

For R^(II4), examples of the halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom.

For R^(II4), examples of a halogen-containing alkyl group include aperfluoromethyl group and a perfluoroethyl group.

For A^(II1), examples of the divalent connecting group include a C1-C18divalent saturated hydrocarbon group in which a methylene group can bereplaced by —O—, —S— or —CO—. Specific examples of the divalentconnecting group include the same saturated hydrocarbon grouprepresented by X^(III3).

Examples of cation of the structural unit represented by formula(II-1-1) include the following ones.

Examples of the organic anion represented by A⁻ include a sulfonateanion, a sulfonylimide anion, a sulfonylmethide anion and a carboxyloxyanion.

Among them, a sulfonate anion is preferred. For A⁻, a sulfonate anion ispreferably the same one as used for the salt represented by formula(B1).

For A⁻, examples of a sulfonylimide anion include the following ones.

For A⁻, examples of a sulfonylmethide anion include the following ones.

For A⁻, examples of a carbonyloxy anion include the following ones.

Examples of the structural unit represented by formula (II-1-1) includethe following ones.

When Resin (A) has the structural unit (II), its content is preferably 1to 20% by mole, more preferably 2 to 15% by mole, still more preferably3 to 10% by mole, based on 100% by mole of all the structural 5 units ofthe resin.

Resin (A) is preferably one which consists of a structural unit (a1) anda structural unit (s).

The structural unit (a1) is preferably one selected from the groupconsisting of the structural unit (a1-0), the structural unit (a1-1) andthe structural unit (a1-2), particularly that is one having a cyclohexylgroup or a cyclopentyl group. More preferably, Resin (A) has twostructural units selected from the group consisting of the structuralunit (a1-0), the structural unit (a1-1) and the structural unit (a1-2),particularly that is one having a cyclohexyl group or a cyclopentylgroup.

The structural unit (s) is preferably one selected from the groupconsisting of the structural unit (a2) and the structural unit (a3). Thestructural unit (a2) is preferably the structural unit (a2-A) or (a2-1).The structural unit (a3) is preferably the structural unit (a3-1), thestructural unit (a3-2) and the structural unit (a3-4).

Resin (A) can be produced according to known polymerization methods suchas radical polymerization.

The resin has usually 2,000 or more of the weight-average molecularweight, preferably 2,500 or more of the weight-average molecular weight,more preferably 3,000 or more of the weight-average molecular weight.The resin has usually 50,000 or less of the weight-average molecularweight, more preferably 30,000 or less of the weight-average molecularweight, and more preferably 15,000 or less of the weight-averagemolecular weight.

The weight-average molecular weight can be measured with gel permeationchromatography.

The composition of the present disclosure may have another resin thanResin (A).

Another resin than Resin (A) comprises no structural unit (a1).

Another resin than Resin (A) may comprise the structural unit (a2), thestructural unit (a3), the structural unit (a4) and the structural unit(a5).

Examples of another resin than Resin (A) include one which comprises thestructural unit (a4) or which consists of the structural unit (a4) andthe structural unit (a5) [these resins are collectively referred to as“Resin (X)” ].

In Resin (X), the content of the structural unit (a4) is preferably 30%by mole or more, more preferably 40% by mole or more, still morepreferably 45% by mole or more based on the sum of the structural unitsin the resin.

Resin (X) usually has 6000 or more of the weight-average molecularweight, preferably 7000 or more of the weight-average molecular weight.The resin usually has 80,000 or less of the weight-average molecularweight, preferably has 60,000 or less of the weight-average molecularweight.

The weight-average molecular weight can be measured with known methodssuch as liquid chromatography or gas chromatography.

When the photoresist composition contains Resin (X), the content of theresin is preferably 1 to 60 weight parts, more preferably 1 to 50 weightparts, and still more preferably 1 to 40 weight parts, further morepreferably 1 to 30 weight parts, further still more preferably 1 to 8weight parts, relative to 100 parts of Resin (A).

The total content of the resins in the photoresist composition of thepresent invention is usually 80% by mass or more, preferably 90% by massor more, based on the sum of solid components, and usually 99% by massor less based on the sum of solid components. In this specification,“solid component” means components other than a solvent in thephotoresist composition.

The resin can be obtained by conducting polymerization reaction of thecorresponding monomer or monomers. The polymerization reaction isusually carried out in the presence of a radical initiator.

This polymerization reaction can be conducted according to knownmethods.

<Solvent>

Preferably, the photoresist composition of the disclosure furthercontains a solvent.

The amount of the solvent is usually 90% by weight or more, preferably92% by weight or more preferably 94% by weight or more based on totalamount of the photoresist composition of the present invention. Theamount of the solvent is usually 99.9% by weight or less and preferably99% by weight or less based on total amount of the photoresistcomposition of the present invention. The content can be measured withknown methods such as liquid chromatography or gas chromatography.

Examples of the solvent include a glycol ether ester such as ethylcellosolve acetate, methyl cellosolve acetate and propylene glycolmonomethyl ether acetate; a glycol ether such as propylene glycolmonomethyl ether; an ester such as ethyl lactate, butyl acetate, amylacetate and ethyl pyruvate; a ketone such as acetone, methyl isobutylketone, 2-heptanone and cyclohexanone; and a cyclic ester such asy-butyrolactone.

<Quencher>

The photoresist composition of the disclosure may further contain aquencher such as a basic compound. The “quencher” has the property thatit can trap an acid, especially an acid generated from the acidgenerator by exposure to light for lithography.

Examples of the quencher include a basic compound, such as a basicnitrogen-containing organic compound, and a salt which generates an acidhaving acidity weaker than an acid generated from the acid generators.

Examples of the basic nitrogen-containing organic compound include anamine compound such as an aliphatic amine, an aromatic amine and anammonium salt. Examples of the aliphatic amine include a primary amine,a secondary amine and a tertiary amine. Examples of the aromatic amineinclude an aromatic amine.

Examples of the quencher include 1-naphthylamine, 2-naphthylamine,aniline, diisopropylaniline, 2-, 3- or 4-methylaniline, 4-nitroaniline,N-methylaniline, N,N-dimethylaniline, diphenylamine, hexylamine,heptylamine, octylamine, nonylamine, decylamine, dibutylamine,pentylamine, dioctylamine, triethylamine, trimethylamine,tripropylamine, tributylamine, tripentylamine, trihexylamine,triheptylamine, trioctylamine, trinonylamine, tridecylamine,methyldibutylamine, methyldipentylamine, methyldihexylamine,methyldicyclohexylamine, methyldiheptylamine, methyldioctylamine,methyldinonylamine, methyldidecylamine, ethyldibutylamine,ethyldipentylamine, ethyldihexylamine, ethyldiheptylamine,ethyldioctylamine, ethyldinonylamine, ethyldidecylamine,dicyclohexylmethylamine, tris [2-(2-methoxyethoxy)ethyl]amine,triisopropanolamine, ethylenediamine, tetramethylenediamine,hexamethylenediamine, 4,4-diamino-1,2-diphenylethane,4,4-diamino-3,3′-dimethyldiphenylmethane,4,4′-diamino-3,3′-diethyldiphenyl methane, piperazine, morpholine,piperidine, hindered amine compound having a piperidine structure,2,2′-methylenebisaniline, imidazole, 4-methylimidazole, pyridine,4-methylpyridine, 1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane,1,2-di(2-pyridyl)ethene, 1,2-di(4-pyridyl)ethene, 1,3-di(4-pyridyl)propane, 1,2-di(4-pyridyloxy) ethane, di(2-pyridyl)ketone,4,4′-dipyridyl sulfide, 4,4′-dipyridyl disulfide, 2,2′-dipyridylamine,2,2′-dipicolylamine and bipyridine.

Examples of the quaternary ammonium hydroxide includetetramethylammonium hydroxide, tetrabutylammonium hydroxide,tetrahexylammonium hydroxide, tetraoctylammonium hydroxide,phenyltrimethylammonium hydroxide,(3-trifluoromethylphenyl)trimethylammonium hydroxide and(2-hydroxyethyl)trimethylammonium hydroxide (so-called “choline”).

As to salt which generates an acid having acidity weaker than an acidgenerated from the acid generators, the acidity in the salts is shown bythe acid dissociation constant (pKa).

The acid dissociation constant of acid generated from the salt for aquencher is usually -3<pKa.

The salt for a quencher is preferably a salt of -1<pKa<7, and morepreferably a salt of 0<pKa<5.

Specific examples of the salt for a quencher include the following ones,an onium carboxylic acid salt such as the salt of formula (D), and saltsrecited in US2012/328986A1, US2011/171576A1, US2011/201823A1,JP2011-39502A1, and US2011/200935A1.

The photoresist composition comprises preferably onium carboxylic acidsalt, more preferably the salt of formula (D).

In formula (D), R^(D1) and R^(D2) respectively represent a C1-C12monovalent hydrocarbon group, a C1-C6 alkoxy group, a C2-C7 acyl group,a C2-C7 acyloxy group, a C2-C7 alkoxycarbonyl group, a nitro group or ahalogen atom. The symbols m′ and n′ each independently represent aninteger of 0 to 4, preferably an integer of 0 to 2, more preferably 0.

Examples of the compounds represented by formula (D) include thefollowing ones.

The content of quencher is preferably 0.01 to 5% by mass, morepreferably 0.01 to 4% by mass, still more preferably 0.01 to 3% by mass,and further more preferably 0.01 to 1% by mass, based on sum of solidcomponent.

The photoresist compositions of the present invention may comprise, ifnecessary, a small amount of various additives such as a sensitizer, adissolution inhibitor, other polymers, a surfactant, a stabilizer and adye as long as the effect of the present invention is not prevented.

The photoresist compositions of the present invention can be prepared bymixing, usually in a solvent, an acid generator which contains Salt (aa)and Resin (A), and if necessary a quencher, and/or additives at asuitable ratio for the composition, optionally followed by filtratingthe mixture with a filter having 0.003m to 0.2m of a pore size.

The order of mixing these components is not limited to any specificorder. The temperature at mixing the components is usually 10 to 40° C.,which can be selected in view of the resin or the like.

The mixing time is usually 0.5 to 24 hours, which can be selected inview of the temperature. The means for mixing the components is notlimited to specific one. The components can be mixed by being stirred.

The amounts of the components in the photoresist compositions can beadjusted by selecting the amount to be used for production of them.

The photoresist compositions of the disclosure are useful for achemically amplified photoresist composition.

A photoresist pattern can be produced by the following steps (1) to (5):

(1) a step of applying the photoresist composition of the presentinvention on a substrate,

(2) a step of forming a composition film by conducting drying,

(3) a step of exposing the composition film to radiation,

(4) a step of baking the exposed composition film, and

(5) a step of developing the baked composition film.

The applying of the photoresist composition on a substrate is usuallyconducted using a conventional apparatus such as spin coater. Examplesof the substrate include a silicon wafer or a quartz wafer on which asensor, a circuit, a transistor or the like is formed.

The formation of the composition film is usually conducted using aheating apparatus such as hot plate or a decompressor, and the heatingtemperature is usually 50 to 200° C. When the pressure is reduced duringheating, the operation pressure is usually 1 to 1.0*10⁵ Pa. The heatingtime is usually 10 to 180 seconds.

The composition film obtained is exposed to radiation using an exposuresystem. The exposure is usually conducted through a mask having apattern corresponding to the desired photoresist pattern. Examples ofthe exposure source include a light source radiating laser light in aUV-region such as a KrF excimer laser (wavelength: 248 nm), an ArFexcimer laser (wavelength: 193 nm) and a F₂ laser (wavelength: 157 nm),a light source radiating harmonic laser light in a far UV region or avacuum UV region by wavelength conversion of laser light from a solidlaser light source (such as YAG or semiconductor laser), and a lightsource radiating electron beam or EUV (extreme ultraviolet) light.

The temperature of baking of the exposed composition film is usually 50to 200° C., and preferably 70 to 150° C.

The development of the baked composition film is usually carried outusing a development apparatus. The development method includes dippingmethods, paddle methods, spray methods and dynamic dispense method. Thedeveloping temperature is preferably 5 to 60° C., and the developingtime is preferably 5 to 300 seconds.

The positive and negative type photoresist patterns can be obtained bythe development depending on a developer to be used therefor.

When a positive type photoresist pattern is prepared from thephotoresist composition of the present invention, the development can beconducted with an alkaline developer. The alkaline developer to be usedmay be any one of various alkaline aqueous solution used in the art.Generally, an aqueous solution of tetramethylammonium hydroxide or(2-hydroxyethyl)trimethylammonium hydroxide (commonly known as“choline”) is often used. The alkaline developer may comprise asurfactant.

After development, the photoresist film having photoresist pattern ispreferably washed with ultrapure water, and the remained water on thephotoresist film and the substrate is preferably removed therefrom.

When a negative type photoresist pattern is prepared from thephotoresist composition of the present invention, the development can beconducted with a developer containing an organic solvent, such developeris sometimes referred to as “organic developer”.

Examples of an organic solvent for organic developer include ketonesolvents such as 2-hexanone, 2-heptanone; glycolether ester solventssuch as propyleneglycolmonomethylether acetate; ester solvents such asbutyl acetate; glycolether solvents such aspropyleneglycolmonomethylether; amide solvents such asN,N-dimethylacetamide; and aromatic hydrocarbon solvents such asanisole.

The content of organic solvent is preferably from 90% to 100% by weight,more preferably from 95% to 100% by weight, in an organic developer.Preferred is that the organic developer essentially consists of anorganic solvent.

Among them, the organic developer is preferably a developer comprisingbutyl acetate and/or 2-heptanone.

The total content of butyl acetate and 2-heptanone is preferably from90% to 100% by weight, more preferably from 95% to 100% by weight.Preferred is that the organic developer essentially consists of butylacetate and/or 2-heptanone.

The organic developer may comprise a surfactant or a very small amountof water.

Development with an organic developer can be stopped by replacing thedeveloper by other solvent than it such as alcohol.

The photoresist composition of the present invention is suitable for KrFexcimer laser lithography, ArF excimer laser lithography, EUV (extremeultraviolet) lithography, EUV immersion lithography and EB (electronbeam) lithography.

EXAMPLES

The invention of the disclosure will be described more specifically byExamples, which are not construed to limit the scope of the presentinvention.

The “%” and “part(s)” used to represent the content of any component andthe amount of any material used in the following examples andcomparative examples are on a weight basis unless otherwise specificallynoted.

The weight-average molecular weight of any material used in thefollowing examples is a value found by gel permeation chromatographyunder the following conditions.

Column: HLC-8120GPC Type (Three Columns with guard column), TSKgelMultipore HXL-M, manufactured by TOSOH CORPORATION

Solvent: Tetrahydrofuran, Flow rate: 1.0 mL/min.

Detector: RI detector

Column temperature: 40° C.

Injection volume: 100 μL

Standard reference material: Standard polystyrene

Structures of compounds were determined by mass spectrometry (LiquidChromatography: 1100 Type, manufactured by AGILENT TECHNOLOGIES LTD.,Mass Spectrometry: LC/MSD Type, manufactured by AGILENT TECHNOLOGIESLTD.).

Example 1

In a reactor, 7 parts of the salt represented by the formula (I-1-a),6.5 parts of the compound represented by the formula (I-1-b), 35 partsof chloroform, 14 parts of acetonitrile and 14 parts ofdimethylformamide were mixed and stirred at 23° C. for 30 minutes.

Then 0.07 parts of p-toluenesulfonic acid was added and then refluxedwhile being stirred for 3 hours. The obtained mixture was cooled to 23°C., and then 155 parts of chloroform was added thereto, followed bybeing filtrated. To the obtained filtrates, 40 parts of 5% aqueoussodium carbonate hydrate solution was added and stirred at 23° C. for 30minutes. Then the obtained mixture was set still to separate an organiclayer therefrom.

To the obtained organic layer, 45 parts of ion-exchanged water wereadded and then stirred at 23° C. for 30 minutes, followed by separatingan organic layer therefrom. The organic layer was washed with water inthe above-mentioned manner three times.

To the obtained organic layer, 95 parts of ethyl acetate was added andthe obtained mixture was stirred. Then a supernatant was removedtherefrom. The obtained residue was dissolved in acetonitrile and thenthe obtained solution was concentrated to give 4.38 parts of the saltrepresented by formula (I-1-c).

In a reactor, 4.34 parts of the salt represented by the formula (I-1-c),50 parts of chloroform and 1.28 parts of pyridine were mixed and stirredat 23° C. for 30 minutes.

Then 3.79 parts of the compound represented by the formula (I-1-d) wasadded and then stirred at 23° C. for 12 hours.

To the obtained mixture, 20 parts of ion-exchanged water were added andthen stirred at 23° C. for 30 minutes. Then the obtained mixture was setstill to separate an organic layer therefrom.

To the obtained organic layer, 15 parts of 5% aqueous oxalic acidsolution were added and then stirred at 23° C. for 30 minutes, followedby separating an organic layer therefrom.

To the obtained mixture, 20 parts of ion-exchanged water were added andthen stirred at 23° C. for 30 minutes, followed by separating an organiclayer therefrom. The organic layer was washed with water in theabove-mentioned manner three times.

To the obtained organic layer, 1 part of acetonitrile and 30 parts oftert-butylmethylether were added and the obtained mixture was stirred.Then a supernatant was removed therefrom. The obtained residue wasdissolved in acetonitrile and then the obtained solution wasconcentrated to give 4.22 parts of the salt represented by formula(I-1).

MASS (ESI(+), spectrum): M⁺ 263.1

MASS (ESI(−), spectrum): M⁻ 467.1

Examples 2

In a reactor, 7.18 parts of the salt represented by the formula(I-10-a), 6.5 parts of the compound represented by the formula (I-1-b),35 parts of chloroform, 14 parts of acetonitrile and 14 parts ofdimethylformamide were mixed and stirred at 23° C. for 30 minutes.

Then 0.07 parts of p-toluenesulfonic acid was added and then refluxedwhile being stirred for 3 hours. The obtained mixture was cooled to 23°C., and then 155 parts of chloroform was added thereto, followed bybeing filtrated. To the obtained filtrates, 40 parts of 5% aqueoussodium carbonate hydrate solution was added and stirred at 23° C. for 30minutes. Then the obtained mixture was set still to separate an organiclayer therefrom.

To the obtained organic layer, 45 parts of ion-exchanged water wereadded and then stirred at 23° C. for 30 minutes, followed by separatingan organic layer therefrom. The organic layer was washed with water inthe above-mentioned manner three times.

To the obtained organic layer, 95 parts of ethyl acetate was added andthe obtained mixture was stirred. Then a supernatant was removedtherefrom. The obtained residue was dissolved in acetonitrile and thenthe obtained solution was concentrated to give 4.62 parts of the saltrepresented by formula (I-10-c).

In a reactor, 4.43 parts of the salt represented by the formula(I-10-c), 50 parts of chloroform and 1.28 parts of pyridine were mixedand stirred at 23° C. for 30 minutes.

Then 3.79 parts of the compound represented by the formula (I-1-d) wasadded and then stirred at 23° C. for 12 hours.

To the obtained mixture, 20 parts of ion-exchanged water were added andthen stirred at 23° C. for 30 minutes. Then the obtained mixture was setstill to separate an organic layer therefrom.

To the obtained organic layer, 15 parts of 5% aqueous oxalic acidsolution were added and then stirred at 23° C. for 30 minutes, followedby separating an organic layer therefrom.

To the obtained mixture, 20 parts of ion-exchanged water were added andthen stirred at 23° C. for 30 minutes, followed by separating an organiclayer therefrom. The organic layer was washed with water in theabove-mentioned manner three times.

To the obtained organic layer, 1 part of acetonitrile and 30 parts oftert-butylmethylether were added and the obtained mixture was stirred.Then a supernatant was removed therefrom. The obtained residue wasdissolved in acetonitrile and then the obtained solution wasconcentrated to give 3.89 parts of the salt represented by formula(I-10).

MASS (ESI(+), spectrum): M⁺ 263.1

MASS (ESI(−), spectrum): M⁻ 481.1

Example 3

In a reactor, 6.69 parts of the salt represented by the formula(I-49-a), 6.5 parts of the compound represented by the formula (I-1-b),35 parts of chloroform, 14 parts of acetonitrile and 14 parts ofdimethylformamide were mixed and stirred at 23° C. for 30 minutes.

Then 0.07 parts of p-toluenesulfonic acid was added and then refluxedwhile being stirred for 3 hours. The obtained mixture was cooled to 23°C., and then 155 parts of chloroform was added thereto, followed bybeing filtrated. To the obtained filtrates, 40 parts of 5% aqueoussodium carbonate hydrate solution was added and stirred at 23° C. for 30minutes. Then the obtained mixture was set still to separate an organiclayer therefrom.

To the obtained organic layer, 45 parts of ion-exchanged water wereadded and then stirred at 23° C. for 30 minutes, followed by separatingan organic layer therefrom. The organic layer was washed with water inthe above-mentioned manner three times.

To the obtained organic layer, 95 parts of ethyl acetate was added andthe obtained mixture was stirred. Then a supernatant was removedtherefrom. The obtained residue was dissolved in acetonitrile and thenthe obtained solution was concentrated to give 4.44 parts of the saltrepresented by formula (I-49-c).

In a reactor, 4.18 parts of the salt represented by the formula(I-49-c), 50 parts of chloroform and 1.28 parts of pyridine were mixedand stirred at 23° C. for 30 minutes. Then 3.79 parts of the compoundrepresented by the formula (I-1-d) was added and then stirred at 23° C.for 12 hours. To the obtained mixture, 20 parts of ion-exchanged waterwere added and then stirred at 23° C. for 30 minutes. Then the obtainedmixture was set still to separate an organic layer therefrom. To theobtained organic layer, 15 parts of 5% aqueous oxalic acid solution wereadded and then stirred at 23° C. for 30 minutes, followed by separatingan organic layer therefrom.

To the obtained mixture, 20 parts of ion-exchanged water were added andthen stirred at 23° C. for 30 minutes, followed by separating an organiclayer therefrom. The organic layer was washed with water in theabove-mentioned manner three times.

To the obtained organic layer, 1 part of acetonitrile and 30 parts oftert-butylmethylether were added and the obtained mixture was stirred.Then a supernatant was removed therefrom. Then the obtained residueswere concentrated to give 4.08 parts of the salt represented by formula(I-49).

MASS (ESI(+), spectrum): M⁺ 237.1

MASS (ESI(−), spectrum): M⁻ 467.1

Example 4

In a reactor, 6.87 parts of the salt represented by the formula(I-58-a), 6.5 parts of the compound represented by the formula (I-1-b),35 parts of chloroform, 14 parts of acetonitrile and 14 parts ofdimethylformamide were mixed and stirred at 23° C. for 30 minutes.

Then 0.07 parts of p-toluenesulfonic acid was added and then refluxedwhile being stirred for 3 hours. The obtained mixture was cooled to 23°C., and then 155 parts of chloroform was added thereto, followed bybeing filtrated. To the obtained filtrates, 40 parts of 5% aqueoussodium carbonate hydrate solution was added and stirred at 23° C. for 30minutes. Then the obtained mixture was set still to separate an organiclayer therefrom.

To the obtained organic layer, 45 parts of ion-exchanged water wereadded and then stirred at 23° C. for 30 minutes, followed by separatingan organic layer therefrom. The organic layer was washed with water inthe above-mentioned manner three times.

To the obtained organic layer, 95 parts of ethyl acetate was added andthe obtained mixture was stirred. Then a supernatant was removedtherefrom. The obtained residue was dissolved in acetonitrile and thenthe obtained solution was concentrated to give 4.55 parts of the saltrepresented by formula (I-58-c).

In a reactor, 4.27 parts of the salt represented by the formula(I-58-c), 50 parts of chloroform and 1.28 parts of pyridine were mixedand stirred at 23° C. for 30 minutes. Then 3.79 parts of the compoundrepresented by the formula (I-1-d) was added and then stirred at 23° C.for 12 hours. To the obtained mixture, 20 parts of ion-exchanged waterwere added and then stirred at 23° C. for 30 minutes. Then the obtainedmixture was set still to separate an organic layer therefrom. To theobtained organic layer, 15 parts of 5% aqueous oxalic acid solution wereadded and then stirred at 23° C. for 30 minutes, followed by separatingan organic layer therefrom.

To the obtained mixture, 20 parts of ion-exchanged water were added andthen stirred at 23° C. for 30 minutes, followed by separating an organiclayer therefrom. The organic layer was washed with water in theabove-mentioned manner three times.

To the obtained organic layer, 1 part of acetonitrile and 30 parts oftert-butylmethylether were added and the obtained mixture was stirred.Then a supernatant was removed therefrom. Then the obtained residueswere concentrated to give 3.39 parts of the salt represented by formula(I-58).

MASS (ESI(+), spectrum): M⁺ 237.1

MASS (ESI(−), spectrum): M 481.1

Example 5

In a reactor, 6.07 parts of the salt represented by the formula(I-53-a), 6.5 parts of the compound represented by the formula (I-1-b),35 parts of chloroform, 14 parts of acetonitrile and 14 parts ofdimethylformamide were mixed and stirred at 23° C. for 30 minutes.

Then 0.07 parts of p-toluenesulfonic acid was added and then refluxedwhile being stirred for 3 hours. The obtained mixture was cooled to 23°C., and then 155 parts of chloroform was added thereto, followed bybeing filtrated. To the obtained filtrates, 40 parts of 5% aqueoussodium carbonate hydrate solution was added and stirred at 23° C. for 30minutes. Then the obtained mixture was set still to separate an organiclayer therefrom.

To the obtained organic layer, 45 parts of ion-exchanged water wereadded and then stirred at 23° C. for 30 minutes, followed by separatingan organic layer therefrom. The organic layer was washed with water inthe above-mentioned manner three times.

To the obtained organic layer, 95 parts of ethyl acetate was added andthe obtained mixture was stirred. Then a supernatant was removedtherefrom. The obtained residue was dissolved in acetonitrile and thenthe obtained solution was concentrated to give 4.62 parts of the saltrepresented by formula (I-53-c).

In a reactor, 3.86 parts of the salt represented by the formula(I-53-c), 50 parts of chloroform and 1.28 parts of pyridine were mixedand stirred at 23° C. for 30 minutes. Then 3.79 parts of the compoundrepresented by the formula (I-1-d) was added and then stirred at 23° C.for 12 hours. To the obtained mixture, 20 parts of ion-exchanged waterwere added and then stirred at 23° C. for 30 minutes. Then the obtainedmixture was set still to separate an organic layer therefrom. To theobtained organic layer, 15 parts of 5% aqueous oxalic acid solution wereadded and then stirred at 23° C. for 30 minutes, followed by separatingan organic layer therefrom.

To the obtained mixture, 20 parts of ion-exchanged water were added andthen stirred at 23° C. for 30 minutes, followed by separating an organiclayer therefrom. The organic layer was washed with water in theabove-mentioned manner three times.

To the obtained organic layer, 1 part of acetonitrile and 30 parts oftert-butylmethylether were added and the obtained mixture was stirred.Then a supernatant was removed therefrom. Then the obtained residueswere concentrated to give 4.08 parts of the salt represented by formula(I-53).

MASS (ESI(+), spectrum): M⁺ 237.1

MASS (ESI(−), spectrum): M⁻ 415.1

Synthesis of Resin

Monomers used in the following synthesis example are shown as follow.

Those monomers are sometimes referred to as “Monomer (X)” in which (X)represents the sign of the formula corresponding to the monomer.

For example, the monomer represented by formula (a1-1-3) is referred toas “Monomer (a1-1-3)”

Synthesis Example 1

To the monomers (a1-1-3), (a1-2-6), (a2-1-1) and (a3-4-2) mixed in amolar ratio of 45/14/2.5/38.5 (monomer (a1-1-3)/monomer (a1-2-6)/monomer(a2-1-1)/monomer (a3-4-2)), propyleneglycolmonomethylether acetate wasadded in 1.5 times amount [based on mass] of the total parts of allmonomers to prepare a mixture. To the mixture, azobisisobutyronitrileand azobis (2,4-dimethylvaleronitrile) were added as an initiator in aratio of 1 mol % and 3 mole % respectively based on all monomer molaramount, and the obtained mixture was heated at 73° C. for about 5 hours.

The reaction mixture as obtained was poured into a large amount of amixture of methanol and water to precipitate resin, followed by beingfiltrated.

Then the filtrates as obtained were dissolved inpropyleneglycolmonomethylether acetate and then the solution of thefiltrates was poured into a mixture of methanol and water toreprecipitate resin. The reprecipitation step was conducted twice.

As a result, a polymer having a weight-average molecular weight of about7800 was obtained in a yield of 69%. The polymer had the followingstructural units. That polymer is referred to as resin A1.

Resin Synthesis Example 2

The monomers (a5-1-1) and (a4-0-12) were mixed in a ratio of 50:50 andmethylisobutylketone was added in 1.2 times amount of the total parts ofall monomers to prepare a solution. To the solution, azobis(2,4-dimethylvaleronitrile) was added as an initiator in a ratio of 3mol % based on all monomer molar amount, and the obtained mixture washeated at 70° C. for about 5 hours.

The reaction mixture as obtained was poured into a large amount of amixture of methanol and water to precipitate resin, followed by beingfiltrated.

As a result, a polymer having a weight-average molecular weight of about10,000 was obtained in a yield of 91%. The polymer had the followingstructural units. That polymer is referred to as resin X1.

Examples 6 to 17 and Comparative Examples 1 to 3

<Producing Photoresist Compositions>

The following components as listed in the following table were mixed anddissolved in the solvent as mentioned below, and then filtrated througha fluorine resin filter having pore diameter of 0.2 μm, to preparephotoresist compositions.

TABLE 4 Resin Acid Salt (I) Quencher (kind/ generator (kind/ (kind/Comp. amount (kind/amount amount amount PB(° C.)/ No. (part)) (part))(part)) (part)) PEB (° C.)  1 X1/0.2 — I-1/0.9 D1/0.28 90/85 A1/10  2X1/0.2 — I-10/0.9 D1/0.28 90/85 A1/10  3 X1/0.2 B1-21/0.55 I-1/0.4D1/0.28 90/85 A1/10 B1-22/0.45  4 X1/0.2 B1-21/0.55 I-10/0.4 D1/0.2890/85 A1/10 B1-22/0.45  5 X1/0.2 — I-49/0.9 D1/0.28 90/85 A1/10  6X1/0.2 — I-58/0.9 D1/0.28 90/85 A1/10  7 X1/0.2 — I-49/1.4 D1/0.28 90/85A1/10  8 X1/0.2 — I-58/1.4 D1/0.28 90/85 A1/10  9 X1/0.2 B1-21/0.55I-49/0.4 D1/0.28 90/85 A1/10 B1-22/0.45 10 X1/0.2 B1-21/0.55 I-58/0.4D1/0.28 90/85 A1/10 B1-22/0.45 11 X1/0.2 — I-53/1.4 D1/0.28 90/85 A1/1012 X1/0.2 B1-21/0.55 I-53/0.4 D1/0.28 90/85 A1/10 B1-22/0.45 Compar.X1/0.2 IX-1/0.9 — D1/0.28 90/85 comp 1 A1/10 Compar. X1/0.2 IX-2/0.9 —D1/0.28 90/85 comp 2 A1/10 Compar. X1/0.2 IX-3/0.9 — D1/0.28 90/85 comp3 A1/10

In Table 4, each of characters represents the following component:

<Resin>

A1: Resin A1, X1: Resin X1

<Salt (I)>

I-1: Salt represented by formula (I-1)

I-10: Salt represented by formula (I-10)

I-49: Salt represented by formula (I-49)

I-53: Salt represented by formula (I-53)

I-58: Salt represented by formula (I-58)

B1-21: Salt represented by formula (B1-21), prepared by the method asrecited in Example of JP2012-224611A1

B1-22: Salt represented by formula (B1-22), prepared by the method asrecited in Example of JP2012-224611A1

IX-1: Salt represented by the following formula, prepared by the methodas recited in Example of JP2011-37837A1

IX-2: Salt represented by the following formula, prepared by the methodas recited in Example of JP2013-256496A1

IX-3: Salt represented by the following formula, prepared by the methodas recited in Example of US2017/0247323A1

<Quencher>

D1: The compound of the following formula, which was manufactured byTokyo Chemical Industries, Co., Ltd.

<Solvent>

Mixture of the following solvents propyleneglycolmonomethylether acetate265 parts propyleneglycolmonomethylether  20 parts 2-Heptanone  20 partst-butyrolactone  3.5 parts

<Producing Photoresist Patterns>

A composition for an organic antireflective film (“ARC-29”, by NissanChemical Co. Ltd.) was applied onto 12-inch silicon wafer and baked for60 seconds at 205° C. to form a 78 nm thick organic antireflective film.

One of the photoresist compositions was then applied thereon by spincoating in such a manner that the thickness of the film after drying(pre-baking) became 85 nm.

The obtained wafer was then pre-baked for 60 seconds on a direct hotplate at the temperature given in the “PB” column in Table 4.

On the wafers on which the photoresist film had thus formed, the filmwas then exposed through a mask for forming contact hole patterns (holepitch 90 nm/hole diameter 55 nm) while changing exposure quantitystepwise, with an ArF excimer laser stepper for liquid-immersionlithography (“XT:1900Gi” by ASML Ltd.: NA=1.35, 3/4 Annular X-Y-pol.lighting). Ultrapure water was used as medium for liquid-immersion.

After the exposure, post-exposure baking was carried out for 60 secondsat the temperature given in the “PEB” column in Table 4. Then,development was carried out with butyl acetate (a product of TokyoChemical Industry Co., LTD) at 23° C. for 20 seconds in the manner ofdynamic dispensing method to obtain a negative photoresist pattern.

<Evaluation as to Critical Dimension Uniformity (CDU)>

The photoresist patterns were formed by the same method as describedabove in which exposure was conducted at the effective sensitivity. Inthis evaluation, the effective sensitivity was determined as theexposure quantity at which the photoresist pattern having 45 nm holediameter was obtained by the exposure using the above-mentioned mask.

The hole diameter was measured at 24 points per one hole of the pattern.The average of the values determined as the hole diameter was defined asthe average hole diameter of the one hole.

As to the average hole diameter, the standard deviation was obtainedbased on the population which consisted of 400 holes within the samewafer. The standard deviation was determined as CDU value.

The results were shown in Table 5. The figures represent standarddeviation values (nm).

TABLE 5 Ex. No. Composition No. CDU value (nm) Ex. 6 1 1.66 Ex. 7 2 1.63Ex. 8 3 1.62 Ex. 9 4 1.60 Ex. 10 5 1.65 Ex. 11 6 1.63 Ex. 12 7 1.60 Ex.13 8 1.59 Ex. 14 9 1.60 Ex. 15 10 1.58 Ex. 16 11 1.67 Ex. 17 12 1.64Comp. Ex. 1 Compar. Comp. 1 1.98 Comp. Ex. 2 Compar. Comp. 2 1.78 Comp.Ex. 3 Compar. Comp. 3 1.82

The salt of the disclosure is useful as a component for a photoresistcomposition, and the photoresist composition containing the salt of thedisclosure can provide photoresist patterns with excellent CDuniformity.

1. A salt comprising a group represented by the formula (aa):

wherein X^(a) and X^(b) independently each represent an oxygen atom or asulfur atom, a ring W represents a C3-C18 heterocycle which has acarbonate ester structure and which can have a substituent, and *represents a binding position.
 2. The salt according to claim 1, whichcomprises a cation and an anion having the group represented by formula(aa).
 3. The salt according to claim 2, wherein the anion having thegroup represented by formula (aa) further has a sulfonate.
 4. The saltaccording to claim 1, which has a group represented by formula (aa1):

wherein X^(a), X^(b), the ring W and * are as defined in claim 1, a ringW1 represents a C3-C18 non-aromatic hydrocarbon ring which can have asubstituent and in which a methylene group can be replaced by —O—, —S—,—CO— or —SO₂—.
 5. The salt according to claim 4, which has an anionrepresented by formula (aa2):

wherein X^(a), X^(b), the ring W and the ring W1 are as defined in claim1, L¹ represents a C1-C24 divalent saturated hydrocarbon group in whicha hydrogen atom can be replaced by a fluorine atom or a hydroxyl groupand in which a methylene group can be replaced by —O— or —CO—, and Q¹and Q² independently each represent a fluorine atom or a C1-C6perfluoroalkyl group.
 6. The salt according to claim 5 wherein the ringW1 represents an adamantane ring or a cyclohexane ring.
 7. The saltaccording to claim 5 wherein L¹ is represented by formula (b1-1) or(b1-2):

in which L^(b2) represents a single bond or a C1-C22 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a fluorineatom; L^(b3) represents a single bond or a C1-C22 divalent saturatedhydrocarbon group where a hydrogen atom may be replaced by a hydroxylgroup or a fluorine atom and where a methylene group may be replaced byan oxygen atom or carbonyl group, provided that total number of thecarbon atoms of L^(b2) and L^(b3) is up to 22; L^(b4) represents aC1-C22 divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a fluorine atom; and L^(b5) represents a single bond or aC1-C22 divalent saturated hydrocarbon group where a hydrogen atom may bereplaced by a hydroxyl group or a fluorine atom and where a methylenegroup may be replaced by an oxygen atom or carbonyl group, provided thatthe total carbon atoms of L^(b4) and L^(b5) is up to
 22. 8. The saltaccording to claim 1 wherein the ring W represents 1,3-dioxan-2-onering.
 9. An acid generator comprising the salt according to claim
 1. 10.A photoresist composition comprising the acid generator according toclaim 9 and a resin which comprises a structural unit having anacid-labile group.
 11. The photoresist composition according to claim 10which further comprises a salt generating an acid weaker in acidity thanan acid generated from the acid generator.
 12. A process for producing aphotoresist pattern comprising the following steps (1) to (5): (1) astep of applying the photoresist composition according to claim 10 or 11on a substrate, (2) a step of forming a composition film by conductingdrying, (3) a step of exposing the composition film to radiation, (4) astep of baking the exposed composition film, and (5) a step ofdeveloping the baked composition film thereby forming a photoresistpattern.